Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, Zaragoza, Spain.
J Phys Condens Matter. 2012 Feb 22;24(7):076006. doi: 10.1088/0953-8984/24/7/076006. Epub 2012 Feb 1.
We report the structural and magnetic properties of the La(1-x)Tb(x)Mn(1/2)Sc(1/2)O(3) series. LaMn(1/2)Sc(1/2)O(3) shows a long range ferromagnetic ordering in agreement with a fully polarized Mn-sublattice. The substitution of La with Tb produces structural changes which affect the magnetic properties. This substitution leads to a contraction in the unit cell volume that mainly reduces the M-O-M bond angle (M = Mn, Sc). The bending of this angle decreases the Mn-O-Mn superexchange interaction and enhances the competition between nearest-neighbour and next-nearest-neighbour interactions. Accordingly, the magnetic ground state changes from ferromagnetic to a glassy magnetic state. Large thermal irreversibility between zero-field-cooled and field-cooled conditions is observed for all samples. The study of the dynamic magnetic properties has been performed using the frequency dependent real part of the ac magnetic susceptibility. The use of both the Vogel-Fulcher law and the conventional critical slowing down law yields similarly good accuracies in the fits. The relaxation times obtained from both laws concur with the existence of a cluster-glass for x ≥ 0.5 samples.
我们报告了 La(1-x)Tb(x)Mn(1/2)Sc(1/2)O(3) 系列的结构和磁性。LaMn(1/2)Sc(1/2)O(3) 表现出长程铁磁有序，与完全极化的 Mn 亚晶格一致。La 被 Tb 取代会产生影响磁性的结构变化。这种取代导致单元体积收缩，主要降低了 M-O-M 键角（M = Mn，Sc）。这个角度的弯曲减少了 Mn-O-Mn 超交换相互作用，并增强了最近邻和次近邻相互作用之间的竞争。因此，磁基态从铁磁态转变为玻璃磁态。所有样品在零场冷却和场冷却条件之间都表现出较大的热不可逆性。使用交流磁化率的频率相关实部研究了动态磁性。Vogel-Fulcher 定律和传统的临界慢化定律的使用都能在拟合中得到很好的精度。这两个定律得到的弛豫时间都与 x ≥ 0.5 样品的团簇玻璃存在相一致。
