Аннотация: The magnetic properties of the superparamagnetic ferrihydrite nanoparticles that form as a result of the vital activity of Klebsiella oxytoca bacteria are studied. Both an initial powder with an average number of iron atoms N Fe ∼ 2000–2500 in a particle and this powder after annealing at 140°C for 3 h in air are investigated. The following substantial modifications of the magnetic properties of the ferrihydrite nanoparticles are detected after annealing: the superparamagnetic blocking temperature increases from 23 to 49.5 K, and the average magnetic moment of a particle increases (as follows from the results of processing of magnetization curves). The particles have antiferromagnetic ordering, and the magnetic moment resulting in the superparamagnetism of the system appears due to random spin decompensation inside the particle. For this mechanism, the number of uncompensated spins is proportional to the number of magnetically active atoms raised to the one-half power, and this relation holds true for the samples under study at a good accuracy. The possible causes of the detected shift of magnetic hysteresis loops at low temperatures upon field cooling are discussed.
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Держатели документа:
Russian Acad Sci, Siberian Branch, Kirenskii Inst Phys, Krasnoyarsk 660041, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, Int Sci Ctr Extreme States Organisms, Siberian Branch, Krasnoyarsk Sci Ctr, Krasnoyarsk 660036, Russia
Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Krasikov, A. A.; Красиков, Александр Александрович; Dubrovskii, A. A.; Дубровский, Андрей Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Bayukov, O. A.; Баюков, Олег Артемьевич; Stolyar, S. V.; Столяр, Сергей Викторович; Iskhakov, R. S.; Исхаков, Рауф Садыкович; Ladygina, V. P.; Ладыгина, Валентина Петровна; Ishchenko, L. A.; Ищенко, Л. А.; Ministry of Education and Science of the Russian Federation; Siberian Branch of the Russian Academy of Sciences