http://dspace.nbuv.gov.ua:80/handle/123456789/115092 2026-04-18T11:35:38Z 2026-04-18T11:35:38Z http://dspace.nbuv.gov.ua:80/handle/123456789/119101 2017-06-05T00:02:48Z 2012-01-01T00:00:00Z

Виктор Валентинович Еременко (к восьмидесятилетию со дня рождения) 26 июля 2012 года исполняется 80 лет со дня рождения академика Виктора Валентиновича Еременко — выдающегося физика: исследователя, педагога, организатора науки.

2012-01-01T00:00:00Z Feher, A. Desnenko, V. Fertman, E. Dolya, S. Kajňaková, M. Beznosov, A. http://dspace.nbuv.gov.ua:80/handle/123456789/117274 2017-05-22T00:03:39Z 2012-01-01T00:00:00Z

Direct evidence of the low-temperature cluster-glass magnetic state of Nd²/₃Ca¹/₃MnO₃ perovskite Feher, A.; Desnenko, V.; Fertman, E.; Dolya, S.; Kajňaková, M.; Beznosov, A. In the presented study we have revealed a giant exchange bias in a colossal magnetoresistance Nd²/₃Ca¹/₃MnO₃ perovskite at low temperatures, evident of an intrinsic exchange coupling in this compound. The phenomena found confirms our previous assumption that the low-temperature magnetic structure of the compound is represented by small (nanosized) ferromagnetic clusters immersed within the charge-ordered antiferromagnetic matrix. Magnetic behavior of the Nd²/₃Ca¹/₃MnO₃ perovskite is consistent with a cluster-glass magnetic state and does not agree with a classical spin-glass state observed in a variety of disordered magnetic systems. We think that the cluster-glass magnetic behavior of Nd²/₃Ca¹/₃MnO₃ originates from the selforganized phase-separated state of the compound. The Cole-Cole analysis of the dynamic susceptibility at lowtemperatures has shown extremely broad distribution of relaxation times, indicating that spins are frozen at a “macroscopic” time scale. Slow relaxation of the zero-field-cooled magnetization has been experimentally revealed as well. This slow relaxation confirms the cluster-glass magnetic state of the compound. Two strongly different relaxation mechanisms were found: the first one is characteristic for temperatures below the freezing temperature Tg ∼ 60 K, the second one is characteristic for higher temperatures.

2012-01-01T00:00:00Z Haines, C.R.S. Marcano, N. Smith, R.P. Aviani, I. Espeso, J.I. Gómez Sal, J.C. Saxena, S.S. http://dspace.nbuv.gov.ua:80/handle/123456789/117273 2017-05-22T00:03:43Z 2012-01-01T00:00:00Z

Complex magnetic states of heavy fermion compound CeGe Haines, C.R.S.; Marcano, N.; Smith, R.P.; Aviani, I.; Espeso, J.I.; Gómez Sal, J.C.; Saxena, S.S. The intermetallic compound CeGe exhibits unusual magnetic behavior due to the interplay between the Kondo and the antiferromagnetic coupling. This particular system is interesting because the Kondo temperature is close to the Néel temperature, resulting in a close competition between the low-temperature interactions, which can be tuned by means of varying external parameters such as pressure and applied magnetic field. Interestingly, magnetization measurements up to 12 kbar reveal that the Néel temperature is not affected by pressure. Measurements of the electrical resistivity, however, show that the sharp upturn appearing below TN is sensitive to pressures up to 15 kbar. This suggests that pressure may change the complex antiferromagnetic spin structure. The validity of an explanation based on the magnetic superzones seen in the rare earths is discussed here.

2012-01-01T00:00:00Z Орел, Е.С. http://dspace.nbuv.gov.ua:80/handle/123456789/117272 2017-05-22T00:03:38Z 2012-01-01T00:00:00Z

Упорядочение в узкозонном магнитном металле с обменным взаимодействием Орел, Е.С. Рассчитана температура магнитного упорядочения ΘC систем с двойным обменом в модели взаимодействующих спиновых волн. Проведен сравнительный анализ с расчетами в модели молекулярного поля и спин-волновой модели. Получен максимум температуры магнитного перехода ΘC при электронной концентрации x = 0,35, что лучше согласуется с экспериментом (x = 0,33), чем расчеты ΘC в модели молекулярного поля и спин-волновой модели.; Розраховано температуру магнітного впорядкування ΘC систем з подвійним обміном в моделі взаємодіючих спінових хвиль. Проведено порівняльний аналіз з розрахунками в моделі молекулярного поля і спін-хвильової моделі. Отримано максимум температури магнітного переходу ΘC при електронній концентрації x = 0,35, що краще відповідає експерименту (x = 0,33), ніж розрахунки ΘC в моделі молекулярного поля та спін-хвильової моделі.; The temperature of magnetic ordering ΘC of systems with a double exchange is calculated by using the model of interacting spin waves. A comparative analysis is performed with the calculations by the model of molecular field and the spin-wave one. A maximum of the magnetic transition temperature ΘC is obtained for electronic concentration x = 0.35, that agrees with the experiment (x = 0.33) better than the calculations of ΘC in the model of molecular field and the spinwave one.

2012-01-01T00:00:00Z