Rajeesh Kumar N, Karthik R, Vasylechko Leonid, Kalai Selvan R
Department of Physics, Bharathiar University, Coimbatore - 641 046, Tamil Nadu, India.
J Phys Condens Matter. 2020 Jun 3;32(24):245802. doi: 10.1088/1361-648X/ab786e.
The present work offers an insight into the magnetic properties of Mn-rich spinel zinc manganate. Rietveld refinement reveals the formation of ZnMnO where Zn and Mn ions are randomly distributed in the tetrahedral sublattice. DC and AC susceptibility measurement of ZnMnO infers the occurrence of two kinds of transition below 11 K. Paramagnetic to ferrimagnetic transition occur at 10.7 K and ferrimagnetic to spin glass-like transition occurs at 5.8 K. The long-range canted ferrimagnetic ordering is corroborated using modified Lotgering model and calculated the exchange interaction values (J = 5.2 K,J = 5.3 K, J = 14.8 K). Further, the observed shift in freezing temperature with DC magnetic field obeys Almeida-Thouless behaviour and frequency dependence of AC susceptibility follows Vogel-Fulcher law. However, the complete establishment of the canonical spin glass state is denied since the manganese ions occupied at the tetrahedral site is equal to the percolation threshold (=33%). Subsequently, the observed spin glass-like behaviour (5.8 K) below Curie temperature (10.7 K) evidences the reentrant spin glass nature. Similarly, the strong frustration in ZnMnO lattice is observed through the substantial negative value of Curie-Weiss temperature (∼-599 K) and very high frustration factor (f = 56). Overall, the chosen ZnMnO is a highly frustrated magnetic system revealing re-entrant spin-glass behaviour.
本工作深入研究了富锰尖晶石锌锰酸盐的磁性。Rietveld精修揭示了ZnMnO的形成，其中Zn和Mn离子在四面体亚晶格中随机分布。对ZnMnO的直流和交流磁化率测量推断出在11 K以下发生了两种转变。顺磁到亚铁磁转变发生在10.7 K，亚铁磁到自旋玻璃状转变发生在5.8 K。使用改进的Lotgering模型证实了长程倾斜亚铁磁有序，并计算了交换相互作用值（J = 5.2 K，J = 5.3 K，J = 14.8 K）。此外，观察到的冻结温度随直流磁场的变化遵循Almeida-Thouless行为，交流磁化率的频率依赖性遵循Vogel-Fulcher定律。然而，由于占据四面体位置的锰离子等于渗流阈值（=33%），标准自旋玻璃态并未完全形成。随后，在居里温度（10.7 K）以下观察到的自旋玻璃状行为（5.8 K）证明了再入自旋玻璃性质。同样，通过居里-外斯温度的大幅负值（约-599 K）和非常高的失配因子（f = 56）观察到ZnMnO晶格中的强烈失配。总体而言，所选择的ZnMnO是一个高度失配的磁性系统，表现出再入自旋玻璃行为。
