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Автор(ы) : Val'kov V.V., Aksenov S.V.
Заглавие : Fano mechanism of the giant magnetoresistance formation in a spin nanostructure arXiv: 1109.0391 vl :
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kalinin Y.E., Sitnikov A.V., Makagonov V.A., Foshin V.A., Volochaev M. N., Pripechenkov I.M., Perova N.N., Ganshina E.A., Rylkov V.V., Granovsky A.B.
Заглавие : Magnetic properties and magnetoresistance of hybrid multilayer nanostructures {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n
Колич.характеристики :9 с
Место публикации : J. Magn. Magn. Mater. - 2024. - Vol. 604. - Ст.172287. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2024.172287. - ISSN 18734766 (eISSN)
Примечания : Cited References: 36. - The work was carried out with the support of the Ministry of Science and Higher Education of the Russian Federation within the framework of a state assignment (project No. FZGM-2023-0006)
Аннотация: The structural, electrical, magnetic, magneto-optical properties and magnetoresistance of {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayer structures, where n = 50 is the number of bilayers (Co40Fe40B20)34(SiO2)66 nanocomposite and ZnO have been studied. The thicknesses of (Co40Fe40B20)34(SiO2)66 nanocomposite layers as well as ZnO spacers were varied in a wide range. The samples were synthesized by ion-beam sputtering onto glass ceramic substrates. The (Co40Fe40B20)34(SiO2)66 composite have an amorphous structure and the semiconductor ZnO interlayers have a hexagonal crystalline structure with the p63mc symmetry group. The nanocomposite layers containing a ferromagnetic component far from the percolation threshold are in a superparamagnetic state. The presented in the paper data of magnetization, magneto-optical transverse Kerr effect and magnetoresistance indicates that long-range ferromagnetic order does not form down to 77 K both for references ZnO films and studied multilayers with thin and thick ZnO interlayers. An increase in the magneto-optical signal in multilayers compared to references (Co40Fe40B20)34(SiO2)66 composite films has been detected at 1.2 eV. The magnetoresistance of {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayers with thick (32 nm) ZnO interlayers is lower than in reference (Co40Fe40B20)34(SiO2)66 nanocomposite, while at thin ZnO interlayers magnetoresistance is significantly higher and reaches 12 % at temperatures of 77 К. Possible mechanisms of ferromagnetic and antiferromagnetic ordering, enhancement of the magneto-optical response and magnetoresistance in {[(Co40Fe40B20)34(SiO2)66]/[ZnO]}n multilayer nanostructures are discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Gokhfeld D. M.
Заглавие : Developing a concept of an effective field in the intergrain medium of a granular superconductor: Effect of the intragrain Meissner currents and Abrikosov vortices trapped in grains on the magnetotransport properties of a Y-Ba-Cu-O granular HTS
Колич.характеристики :18 с
Место публикации : J. Supercond. Nov. Magn. - 2023. - Vol. 36, Is. 7-9. - P.1631-1648. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-023-06608-2. - ISSN 15571947 (eISSN)
Примечания : Cited References: 58. - The authors are grateful to M.I. Petrov, A.D. Balaev, and V.M. Sosnin for fruitful discussions and A.V. Shabanov and I.V. Nemtsev for scanning electron microscopy investigations. The scanning electron microscopy investigations and a part of magnetic measurements (performed on a LakeShore VSM 8604 facility) were carried out at the Krasnoyarsk Regional Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences. The study is performed within the state assignment of Kirensky Institute of Physics
Аннотация: Granular high-temperature superconductors (HTSs) are characterized by the hysteretic field dependences of magnetoresistance R(H) and critical current IC(H). These hysteretic effects are described within the concept of an effective field in the intergrain medium. The effective field is a superposition of external magnetic field H and the field induced by the magnetic moments of superconducting grains into intergrain spacings (grain boundaries). The magnetization of superconducting grains is determined by two contributions: Meissner (shielding) currents (MC) and trapped magnetic fluxes (Abrikosov vortices (AV)). To develop the concept of an effective field in the intergrain medium, the magnetotransport properties (R and IC) have been compared for two cases: (AV) the magnetization of superconducting grains is only determined by the trapped magnetic flux (zero external field) and (MC) HTS grains are in the Meissner state (the external field is weaker than the first critical field of grains). In a set of experiments, the main features of the hysteretic R(H) and M(H) dependences have been illustrated and the external conditions for implementing the AV and MC states have been established. It has been found that the effects of the Abrikosov vortices and intragrain Meissner currents on an effective field in the intergrain medium at the same magnetization values are noticeably different. This is a nontrivial fact that requires a thorough study of the impact of the anisotropy of the superconducting properties of grains on the configuration of the Meissner currents in them, as well as on the orientation of vortices both inside grains and near their surface. We suggest the explanation of observed stronger effect of the Meissner currents on the intergrain medium as compared with the effect of the Abrikosov vortices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Samoshkina Yu. E., Rautskii M. V., Neznakhin D. S., Stepanova E. A., Edelman I. S., Chou, Hsiung
Заглавие : Particles–matrix bond in ZnCoO:H and ZnCoAlO:H films: Issues of magnetism and spin injection
Место публикации : Materials. - 2023. - Vol. 16, Is. 10. - Ст.3659. - ISSN 19961944 (eISSN), DOI 10.3390/ma16103659
Примечания : Cited References: 45. - This work was supported by the Russian Science Foundation [grant number 21-72-00061]
Аннотация: ZnCoO:H and ZnCoAlO:H films were synthesized by radio frequency magnetron sputtering in a (1 − x)Ar + xH2 mixed atmosphere with x = 0.2–0.5. The films contain different amounts of metallic Co particles (from 7.6% and higher) ~4–7 nm in size. The magnetic and magneto-optical (MO) behavior of the films was analyzed in combination with their structural data. The samples exhibit high values of magnetization (up to 377 emu/cm3) and MO response at room temperature. Two situations are considered: (1) the film magnetism is associated only with isolated metal particles and (2) magnetism is present both in the oxide matrix and in metal inclusions. It has been established that the formation mechanism of the magnetic structure of ZnO:Co2+ is due to the spin-polarized conduction electrons of metal particles and zinc vacancies. It was also found that in the presence of two magnetic components in the films, these components are exchange-coupled. In this case, the exchange coupling generates a high spin polarization of the films. The spin-dependent transport properties of the samples have been studied. A high value of the negative magnetoresistance of the films at room temperature (~4%) was found. This behavior was explained in terms of the giant magnetoresistance model. Thus, the ZnCoO:H and ZnCoAlO:H films with high spin polarization can be considered as sources of spin injection.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smolyakov D. A., Tarasov A. S., Shanidze, Lev, Bondarev I. A., Baron F. A., Lukyanenko A. V., Yakovlev I. A., Volochaev M. N., Volkov N. V.
Заглавие : Effect of magnetic and electric fields on the AC resistance of a silicon-on-insulator-based transistor-like device
Коллективы : RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science [20-42-243007, 20-42-240013]; Government of the Russian Federation; Mega-grant for the Creation of Competitive World-Class Laboratories [075-15-2019-1886]
Место публикации : Phys. Status Solidi A. - 2022. - Vol. 219. Is. 1. - Ст.2100459. - ISSN 1862-6300, DOI 10.1002/pssa.202100459. - ISSN 1862-6319(eISSN)
Примечания : Cited References: 19. - The authors thank the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center of the SB RAS, for electron microscope investigations. This study was supported by RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, projects nos. 20-42-243007 and 20-42-240013, and by the Government of the Russian Federation, the Mega-grant for the Creation of Competitive World-Class Laboratories, agreement no. 075-15-2019-1886
Предметные рубрики: NANOSTRUCTURES
Аннотация: Herein, the AC magnetoresistance (MR) in the silicon-on-insulator (SOI)-based Fe/Si/SiO2/p-Si structure is presented. The structure is used for fabricating a back-gate field-effect pseudo-metal-oxide-semiconductor field-effect transistor (MOSFET) device. The effects of the magnetic field and gate voltage on the transport characteristics of the device are investigated. Magnetoimpedance value of up to 100% is obtained due to recharging of the impurity and surface centers at the insulator/semiconductor interface. A resistance variation of up to 1000% is found, which is caused by the voltage applied to the gate and the field effect on the band structure of the sample. Combining the magnetic and electric fields, one can either change the absolute value of the AC resistance while having the MR fixed or change the sign and character of the field dependence of the MR. The observed effects can be used in the development of magnetic-field-driven SOI-based devices and high-frequency circuits.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Aplesnin S. S., Sitnikov M. N., Udod L. V., Kharkov A. M.
Заглавие : Magnetoresistance and magnetoimpedance in holmium manganese sulfides
Коллективы : Russian Foundation for Fundamental InvestigationsRussian Foundation for Basic Research (RFBR) [20-42-243002]
Место публикации : Appl. Phys. A. - 2022. - Vol. 128, Is. 2. - Ст.124. - ISSN 0947-8396, DOI 10.1007/s00339-021-05198-x. - ISSN 1432-0630(eISSN)
Примечания : Cited References: 46. - Funding was provided by Russian Foundation for Fundamental Investigations (20-42-243002)
Предметные рубрики: PHASE-SEPARATION
IMPEDANCE
Аннотация: The structure, transport characteristics, real and imaginary parts of the impedance components and electric polarization of the HoXMn1-XS (X = 0.1 and 0.2) system have been investigated in the temperature range of 80-500 K in magnetic fields of up to 12 kOe. The morphology of synthesized samples has been studied. The influence of the magnetic field on the transport characteristics, on both direct and alternating currents of holmium manganese sulfides, have been established. The negative effects of DC magnetoresistance in the region of the magnetic phase transition and positive AC magnetoimpedance up to 4% in the paramagnetic region have been established. The critical temperatures of the existence of the electric polarization have been determined. At a substitution concentration of X = 0.1, the activation character of the relaxation time versus temperature has been found. The diffusion contribution for the composition with X = 0.2 has been established by the impedance hodograph.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Gokhfeld D. M.
Заглавие : Influence of intragranular Meissner currents and magnetic flux trapped in granules on the effective field in the intergranular medium and the magnetoresistance hysteresis of a granular HTSC
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 12. - P.1846-1854. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.12.54376.442. - ISSN 10906460 (eISSN)
Примечания : Cited References: 61. - The study was carried out with the financial support of the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, the Krasnoyarsk areal Science Foundation within the framework of the scientific project No. 20-42-240008 ”The effect of the introduction of paramagnetic ions of rare earth elements on the superconducting properties of materials based on YBCO“. The study of the microstructure and magnetic measurements were carried out using the equipment of the Center for Collective Use of the FITC KNC SB RAS
Аннотация: The concept of an effective field in an intergranular medium is used to describe the hysteresis magnetoresistance of granular HTSCs. This effective field is a superposition of the external magnetic field and the field induced by the magnetic moments of the superconducting granules. The magnetic moment of the granules is contributed by the shielding currents and the trapped magnetic flux. We studied and analyzed the effect of the trapped flux on the magnetoresistance. It has been experimentally shown that the dependence of the residual resistance RRem (after applying of the external field) on the trapped flux clearly correlates with the behavior of the remanent magnetization. In addition, special attention was paid to a detailed comparison of the magnetoresistance of the granular YBa2Cu3O7-δ for two cases: (a) the magnetization of HTSC-granules is caused only by the trapped magnetic flux (in a zero external field) and (b) HTSC-granules are in the Meissner state (the external field is smaller than the first critical field of the granules). It has been found that Abrikosov vortices and intragranular Meissner currents differently affect the effective field in the intergranular medium (for the same values (of magnetization for cases (a) and (b) ). A possible reason for this difference is discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A., Petrov M. I.
Заглавие : Universal behavior and temperature evolution of the magnetoresistance hysteresis in granular high-temperature superconductors Y-Ba-Cu-O
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 7. - P.1069-1080. - ISSN 1063-7834, DOI 10.1134/S1063783421070192. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 80. - The authors are grateful to D.M. Gokhfeld for discussion of the results. The measurements of the transport properties were performed in part on a PPMS-6000 system of the Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences
Предметные рубрики: CRITICAL-CURRENT-DENSITY
CURRENT-VOLTAGE CHARACTERISTICS
MAGNETIC-FLUX COMPRESSION
Аннотация: Regularities in the behavior of the magnetoresistance hysteresis R(H) in the granular yttrium high-temperature superconductors (HTSs) have been established. For this purpose, a comparative analysis of the magnetotransport properties has been carried out on the granular HTS samples, which exhibit (i) approximately the same magnetic properties and temperatures of the onset of the superconducting transition (90.5–93.5 K, which is characteristic of HTS grains) and (ii) different critical transport currents JC (which is characteristic of grain boundaries). Despite a significant (by more than an order of magnitude) spread of the JC values for the three samples, a universal behavior of the magnetoresistance hysteresis has been found, which is apparently inherent in all the granular Y–Ba–Cu–O compounds. The R(H) hysteresis is extremely broad and, in a fairly wide external field range, the dependence of the magnetoresistance hysteresis width ΔН on the field Hdec (the external field for the decreasing hysteresis branch is Н = Hdec) is almost linear: ΔH ≈ Hdec. This behavior is observed over the entire temperature range of implementation of the superconducting state (the investigations have been carried out at temperatures of 77–88 and 4.2 K). The result obtained has been explained by considering the effective field in grain boundaries, which is a superposition of the external field and the field induced by the magnetic moments of grains. The field induced by grains, in turn, significantly increases in the region of grain boundaries due to the magnetic flux compression (the grain boundary length is shorter than the HTS grain size by several orders of magnitude). The aforesaid has been confirmed by the analysis of the R(H) hysteresis for the Y–Ba–Cu–O- and CuO-based HTS composite, in which the grain boundary length is purposefully increased; as a result, the flux compression is less pronounced and the R(H) hysteresis narrows.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Aplesnin S. S., Sitnikov M. N., Udod L. V.
Заглавие : Magnetotransport effects and electronic phase separation in manganese sulfides with electron-hole doping
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Belarussian Republic Foundation for Basic Research [20-52-00005]
Место публикации : J. Exp. Theor. Phys. - 2021. - Vol. 132, Is. 5. - P.831-842. - ISSN 1063-7761, DOI 10.1134/S106377612103016X. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 38. - This study was supported by the Russian Foundation for Basic Research and the Belarussian Republic Foundation for Basic Research (project no. 20-52-00005)
Предметные рубрики: MAGNETIC-PROPERTIES
TRANSITION
MAGNETORESISTANCE
Аннотация: We analyze the effect of electron and hole doping with a low substituent concentration (x = 0.01) on the magnetic and electron subsystems in disordered semiconductors MexMn1-xS (Me = Ag and Tm) in a wide range of temperatures (77–1000 K) and magnetic fields up to 12 kOe. Using magnetic measurements, we have established the domains of ferron (polaron) formation in the vicinity of the magnetic phase transition. We have detected the magnetoimpedance and magnetoresistance, the magnitude and sign of which depend on the electric field, temperature, and the type of the substituent element. We have determined the temperatures of thermopower peaks associated with deformation of the crystalline structure. We have established the phonon and magnon contributions to charge carrier relaxation using the method of impedance spectroscopy and the Jahn–Teller mode of oscillations from the IR spectra for the system containing silver. We have determined the diffusion contribution to the conductivity from the impedance hodograph in TmxMn1-xS semiconductors. The experimental results are described using the models of supermagnetic clusters, ferroelectric domains, and the Debye model.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Gokhfel'd D. M., Terent'ev K. Yu., Balaev D. A.
Заглавие : Mechanisms of the magnetoresistance hysteresis in a granular HTS with the paramagnetic contribution by the example of HoBa2Cu3O7-δ
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk krai; Krasnoyarsk Territorial Foundation for Support of Scientific and RD Activities [20-42-240008]
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 12. - P.1785-1794. - ISSN 1063-7834, DOI 10.1134/S1063783421100334. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 72. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk krai, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 20-42-240008 "Effect of introduction of paramagnetic ions of rare-earth elements on the superconducting properties of YBCO materials"
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTOR
MAGNETIC-FLUX COMPRESSION
Аннотация: The hysteretic behavior of magnetoresistance R(H) of the granular high-temperature superconductor (HTS) HoBa2Cu3O7 – δ has been investigated. The YBCO superconductors with a rare-earth element (Nd, Ho, Er, Sm, Yb, or Dy) with the magnetic moment in the yttrium site are characterized by a significant paramagnetic contribution to the total magnetization. The main goal of this study has been to establish the possible effect of this paramagnetic contribution on the magnetotransport properties, which are determined by tunneling of superconducting current carriers through the grain boundaries. An analysis of the results obtained basing on the concept of an effective field in the intergrain medium showed that the distribution of the magnetic induction lines from the paramagnetic moments is fundamentally different from that of the Meissner currents and Abrikosov vortices. The magnetic induction lines from the paramagnetic moments are not concentrated in the region of grain boundaries and therefore insignificantly affect the magnetotransport properties of a granular HTS. At the same time, the magnetic induction lines are strongly concentrated in the grain boundaries, which is caused by the Meissner currents and Abrikosov vortices, due to the features of their properties. Specifically, the magnetic flux compression determines the magnetotransport (in particular, the R(H) hysteresis) properties of granular HTSs, including 1–2–3 ones, with a rare-earth ion with the magnetic moment.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Kretinin V. V., Aplesnin S. S., Sitnikov M. N., Udod L. V., Yanushkevich K. I.
Заглавие : Electrical properties of the polycrystalline BiFe0.95Co0.05O3 films
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Belarusian Republican Foundation for Basic Research [20-52-00005]
Место публикации : Phys. Solid State. - 2021. - Vol. 63. Is. 6. - P.897-903. - ISSN 1063-7834, DOI 10.1134/S1063783421060184. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 34. - This study was supported by the Russian Foundation for Basic Research and the Belarusian Republican Foundation for Basic Research, project no. 20-52-00005
Предметные рубрики: BiFeO3 THIN-FILMS
PHASE-SEPARATION
CRYSTAL
MODEL
Аннотация: Semiconductor BiFe0.95Co0.05O3 thin-film compounds have been synthesized by a burst technique. The film surface morphology and the effect of electronic doping via substitution of cobalt ions for trivalent iron on the optical, magnetic, and kinetic properties have been investigated in the temperature range of 77-600 K in magnetic fields of up to 12 kOe. Two electron relaxation channels have been found in the impedance spectrum in the frequency range of 0.1-1000 kHz. The negative magnetoresistance in the anomalous magnetization region and the maximum magnetoimpedance in the vicinity of the surface phase transition have been established. Using the Hall measurements, carrier types dominating in the magnetoresistance and magnetoimpedance effects have been determined. The magnetization anomalies have been explained in the model of superparamagnetic clusters and the magnetoresistance, by the carrier scattering by spin fluctuations.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vas'kovskiy V. O., Volochaev M. N., Gorkovenko A. N., Kravtsov E. A., Lepalovskij V. N., Feshchenko A. A.
Заглавие : Structural features and magnetic properties of Co-W films
Коллективы : Ministry of Science and Higher Education of the Russian Federation [FEUZ-2020-0051]
Место публикации : Phys. Solid State. - 2021. - Vol. 63. Is. 7. - P.1113-1119. - ISSN 1063-7834, DOI 10.1134/S1063783421070246. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 23. - This work was carried out with support by the Ministry of Science and Higher Education of the Russian Federation, topic no. FEUZ-2020-0051.
Предметные рубрики: GIANT MAGNETORESISTANCE
ANISOTROPY
Аннотация: The structure and magnetic properties of thin polycrystalline films of Co100 – xWx (0 ≤ x ≤ 30) deposited by magnetron sputtering on glass substrates are investigated including those containing buffer layers of Ta, W, and Ru. It is found that films of pure Co are non-single-phase and contain hcp and fcc crystalline modifications. Doping leads to an increase in the concentration of the fcc phase and an enhancement of the texture of the (111) type, and subsequently to the amorphization of the films. The buffer layers influence to a certain extent on the depth and concentration localization of these transformations. A characteristic feature of the magnetism of Co–W films is a significant perpendicular component in the macroscopic magnetic anisotropy, which leads to a “supercritical” magnetic state. It is shown that its source is the textured fcc phase, the crystalline anisotropy of which is enhanced as a result of doping of cobalt with tungsten.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Masyugin A. N., Kretinin V. V., Konovalov S. O., Shestakov N. P.
Заглавие : Magnetoresistance and IR spectrum of impurity states in the Ce3Fe5O12 film
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 2. - P.242-247. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783421020025
Примечания : Cited References: 28. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Krai, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 18-42-240001 “Inversion of the Sign of Magnetoelectric Tensor Components with Temperature in the Neodymium-Doped Bismuth Iron Garnet Films”
Аннотация: In polycrystalline cerium iron garnet films, the gap in the electron excitation spectrum and electronic transitions between di- and tetravalent iron and cerium impurity ions have been established from the IR absorption spectra. The temperatures of delocalization of the ferrous states of iron have been found from the impedance spectroscopy, electrical resistance, and IR spectroscopy data. The difference between the ac and dc magnetoresistances has been established and explained using a model of a dielectrically inhomogeneous medium.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smolyakov D. A., Tarasov A. S., Bondarev M. A., Nikolskaya A. A., Vasiliev V. K., Volochaev M. N., Volkov N. V.
Заглавие : Admittance spectroscopy of dopants implanted in silicon and impurity state-induced AC magnetoresistance effect
Место публикации : Mater. Sci. Semicond. Process. - 2021. - Vol. 126. - Ст.105663. - ISSN 13698001 (ISSN), DOI 10.1016/j.mssp.2021.105663
Примечания : Cited References: 21. - This study was supported by the Government of the Russian Federation , Mega Grant for the Creation of Competitive World-Class Laboratories (Agreement no. 075-15-2019-1886)
Аннотация: A silicon structure doped with Ga using ion implantation has been investigated by admittance spectroscopy. It has been established that the presence of the Ga impurity, along with the B one, in the silicon structure leads to the appearance of the second peak in the temperature dependence of the real part of the impedance (admittance). Moreover, switching-on a magnetic field parallel to the sample plane shifts the singularities in the temperature curve to the high-temperature region. This results in the manifestation of both the positive and negative magnetoresistance effect upon temperature and magnetic field variation. It has been found by the standard admittance spectroscopy analysis of the impedance data that the energy structure of the investigated sample includes two interfacial energy levels ES1(0) = 42 meV and ES2(0) = 69.4 meV. As expected, these energies are consistent with the energies of B and Ga dopants. In a magnetic field, these levels increase by 3 meV for B and 2 meV for Ga, which induces the magnetoresistance effect. It has been demonstrated that the interfacial state-induced magnetoresistance effect can be tuned by ion implantation and dopant selection.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Gokhfeld D. M.
Заглавие : New evidence of interaction between grain and boundaries subsystems in granular high-temperature superconductors
Место публикации : J. Supercond. Novel Magn. - 2021. - Vol. 34. Is. 4. - P.1067-1075. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-021-05812-2
Примечания : Cited References: 62
Аннотация: Granular high-temperature superconductors (HTSs) exhibit magnetotransport properties, including the clockwise magnetoresistance hysteresis. The hysteresis is explained by the concept of an effective field in the subsystem of grain boundaries, where the observed dissipation occurs. The effective field in the intergrain medium is determined by a superposition of the external field H and the field induced by the magnetic response of HTS grains. The magnetic flux compression in the intergrain medium provides an increase of the effective field. The magnetoresistance hysteresis of polycrystalline YBa2Cu3O7-δ has a bright feature: In a fairly wide external field range, the hysteresis width ΔH(H) is found to be almost linear, ΔH ≈ H. This behavior is considered to be universal over the entire temperature range corresponding to the superconducting state (the investigations have been carried out at temperatures of 77 K and 4.2 K). The analysis of the magnetoresistive and magnetic properties has shown that the upper boundary of the field range of the ΔH ≈ H regime is consistent with the field of complete penetration into HTS grains. This is indicative of the strong interrelation between the magnetotransport and magnetic properties of granular HTSs.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Aplesnin S. S., Sitnikov M. N., Udod L. V., Begisheva O. B., Demidenko O. F.
Заглавие : Magnetoresistive effect in the cobalt-doped bismuth ferrite films
Место публикации : J. Mater. Sci.: Mater. Electron. - 2020. - Vol. 31, Is. 10. - P.7946-7952. - ISSN 0957-4522, DOI 10.1007/s10854-020-03333-7. - ISSN 1573-482X(eISSN)
Примечания : Cited References: 39
Предметные рубрики: BIFEO3 THIN-FILMS
ELECTRICAL-PROPERTIES
COFE/CU MULTILAYERS
GIANT MAGNETORESISTANCE
Аннотация: Bismuth ferrite films have been synthesized by the burst-mode deposition of the BiFe0.8Co0.2O3 solid solutions onto object glasses. The surface morphology of the BiFe0.8Co0.2O3 films has been examined. The effect of electron doping implemented by substitution of cobalt for iron in the BiFe0.8Co0.2O3 films on their magnetic, electrical, and galvanomagnetic properties has been investigated at temperatures of 77-600 K in magnetic fields of up to 12 kOe. The negative magnetoresistance has been observed, which changes its sign in the region of formation of magnetically heterogeneous states and attain its maximum value above room temperature. It has been established that the magnetoresistance is caused by the competition of electron hoppings and localization of electrons in a magnetic field. Using the Hall measurements, the carrier type has been determined. A model of the change in the curriers sign upon heating due to the shift of the chemical potential relative to the impurity subband has been proposed.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ma, Yalin, Molokeev M. S., Zhu, Chuanhui, Zhao, Shuang, Han, Yifeng, Wu, Meixia, Liu, Sizhan, Tyson, Trevor A., Croft, Mark, Li, Man-Rong
Заглавие : Magnetic transitions in exotic perovskites stabilized by chemical and physical pressure
Место публикации : J. Mater. Chem. C. - 2020. - Vol. 8, Is. 15. - P.5082-5091. - ISSN 2050-7526, DOI 10.1039/c9tc06976c. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 79. - This work was financially supported by the National Science Foundation of China (NSFC-21801253, 11804404 and 21875287) and the National Science Foundation (NSF) Grant No. DMR-1809931. Structural analysis of exotic materials in this study was partly supported by the Research Grant No. 075-15-2019-1886 from the Government of the Russian Federation. The XANES work at the Brookhaven National Laboratory, NSLS-II, was supported by the DOEBES (DE-SC0012704). The NSLS-II work was performed on beamline 7-BM and the authors gratefully acknowledge the invaluable help of the beamline scientists Steven Ehrlich and Syed Khalid.
Предметные рубрики: COLOSSAL MAGNETORESISTANCE
CATION ORDER
RMN3O6 R
T-C
TEMPERATURE
Аннотация: Exotic perovskites significantly enrich materials for multiferroic and magnetoelectric applications. However, their design and synthesis is a challenge due to the mostly required recipe conditions at extremely high pressure. Herein, we presented the Ca2−xMnxMnTaO6 (0 ≤ x ≤ 1.0) solid solutions stabilized by chemical pressure assisted with intermediate physical pressure up to 7 GPa. The incorporation of Mn2+ into the A-site neither drives any cationic ordering nor modifies the orthorhombic Pbnm structure, namely written as (Ca1−x/2Mnx/2)(Mn1/2Ta1/2)O3 with disordered A and B site cationic arrangements. The increment of x is accompanied by a ferromagnetic to antiferromagnetic transition around x = 0.2, which is attributed to the double-exchange interactions between A-site Mn2+ and B-site Mn3+. Partial charge disproportionation of the B-site Mn3+ into Mn2+ and Mn4+ occurs for x above 0.8 samples as manifested by X-ray spectrum and magnetic behaviors. The coexistence of B-site Mn3+ (Jahn–Teller distortion ion) and B′-site Ta5+ (second-order Jahn–Teller distortion ion) could be energetically responsible for the absence of A-site columnar ordering as observed in other quadruple perovskites with half of the A-sites occupied by small transition-metal cations. These exceptional findings indicate that exotic perovskites can be successfully stabilized at chemical and intermediate physical pressure, and the presence of Jahn–Teller distortion cations at the same lattice should be avoided to enable cationic ordering.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balashev V. V., Ermakov K. S., Samardak A. Y., Ognev A. V., Samardak A. S., Komogortsev S. V., Volochaev M. N., Tarasov A. S., Korobtsov V. V.
Заглавие : Crystal texture-dependent magnetic and magnetotransport properties of half-metallic Fe3O4 films grown on oxidized Si substrates by reactive deposition
Место публикации : J. Alloys Compd. - 2020. - Vol. 815. - Ст.152398. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2019.152398
Примечания : Cited References: 58. - his work is supported in part by the Russian Ministry of Science and Higher Education under the state tasks ( 3.5178.2017/8.9 and 3.4956.2017 ), by Act 211 of the Government of the Russian Federation (contract No. 02.A03.21.0011 ) and by the Comprehensive Program of Basic Research of the Far Eastern Branch of the Russian Academy of Sciences “Far East” 2018–2020 № 18-3-022 ( 0226-18-0031 ).
Аннотация: Nanocrystalline magnetite (Fe3O4) films with various preferred crystallite orientations were grown on oxidized silicon surface by reactive iron deposition in an oxygen atmosphere. Depending on the partial pressure of oxygen (PO2), the evolution of the structural, magnetic, and magnetotransport properties of the grown films was investigated. We found that the growth of films containing only the Fe3O4 phase occurs in a certain PO2 range, and the magnetite crystallites may have (311) or (110) preferred orientation. It was revealed that films with (311) and (110) textures have a column structure. An increase in the PO2 leads to a structure transformation from (311) to (110) texture with larger crystallites. A film with (110) texture showed higher values of saturation magnetization, magnetoresistance and spin polarization. The analysis of approach to magnetic saturation revealed that the local magnetic anisotropy of crystallites in textured films is much higher than the anisotropy of bulk magnetite due to the large surface contribution. The FORC diagram method in combination with the approach to magnetic saturation proved the existence of the exchange coupling between large and small grains. Our results open the reliable route for crystal texture-depending manipulation of functional properties of thin magnetite films for advanced spintronic applications.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volochaev M. N., Granovsky A. B., Zhilova O. V., Kalinin Y. E., Ryl'kov V. V., Sumets M. P., Makagonov V. A., Pankov S. Y., Sitnikov A. V., Fadeev E., Lahderanta E., Foshin V.
Заглавие : Transport and magnetic phenomena in ZnO-С thin-film heterostructures
Место публикации : Superlattices Microstruct. - 2020. - Vol. 140. - Ст.106449. - ISSN 07496036 (ISSN), DOI 10.1016/j.spmi.2020.106449
Примечания : Cited References: 36. - The work was supported by the Ministry of Education and Science of Russia (project No. 3.1867.2017/4.6 ) and the RFBR (project No. 19-07-00471). The work was partially funded by the Academy of Finland
Аннотация: ZnO- and C-based heterostructures were fabricated by the layer-by-layer deposition technique using the ion-beam sputtering process. Structure, electrical and magnetic properties of fabricated heterostructures are discussed. The two-phase (ZnO and C) films are evolved into a multilayer structure, consisting of amorphous carbon and crystalline ZnO layers when the bilayer thickness increases. When carbon is added to ZnO, its electrical resistivity reduces. The conduction mechanism changes from the variable-range hopping in a narrow energy band to the nearest neighbors hopping in ZnO–C films with a thickness of h ˂ 150 nm. The temperature dependence of conductivity changes from the Arrhenius-like to logarithmic law, indicating that the strong charge localization turns into a weak one when the film thickness is about 150 nm. The negative magnetoresistance of up to 1% was detected at 77 K. The film ferromagnetism at the temperature of 10 K was not found.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A.
Заглавие : Model of the behavior of a granular HTS in an external magnetic field: temperature evolution of the magnetoresistance hysteresis
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 7. - P.1136-1144. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420070239
Примечания : Cited References: 61. - The authors are grateful to D.M. Gokhfeld for discussion of the results. The measurements of the transport properties were performed in part on a PPMS-6000 facility at the Krasnoyarsk Territorial Center of Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: A model for describing the magnetoresistance behavior in a granular high-temperature superconductor (HTS) that has been developed in the last decade explains a fairly extraordinary form of the hysteretic R(H) dependences at T = const and their hysteretic features, including the local maximum, the negative magnetoresistance region, and the local minimum. In the framework of this model, the effective field Beff in the intergrain medium has been considered, which represents a superposition of the external field and the field induced by the magnetic moments of HTS grains. This field can be written in the form Beff(H) = H + 4παM(H), where M(H) is the experimental field dependence of the magnetization and α is the parameter of crowding of the magnetic induction lines in the intergrain medium. Therefore, the magnetoresistance is a function of not simply an external field, but also the “internal” effective field R(H) = f(Beff(H)). The magnetoresistance of the granular YBa2Cu3O7 – δ HTS has been investigated in a wide temperature range. The experimental hysteretic R(H) dependences obtained in the high -temperature range (77–90 K) are well explained using the developed model and the parameter α is 20–25. However, at a temperature of 4.2 K, no local extrema are observed, although the expression for Beff(H) predicts them and the parameter α somewhat increases (~30–35) at this temperature. An additional factor that must be taken into account in this model can be the redistribution of the microscopic current trajectories, which also affects the dissipation in the intergrain medium. At low temperatures under the strong magnetic flux compression (α ~ 30–35), the microscopic trajectories of the current Im can change and tunneling through the neighboring grain is preferred, but the angle between Im and Beff will be noticeably smaller than 90°, although the external (and effective) field direction is perpendicular to the macroscopic current direction.
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