Petersburg Nuclear Physics Institute, NRC 'Kurchatov Institute', Orlova Coppice, Gatchina 188300, Russia.
J Phys Condens Matter. 2014 Feb 19;26(7):076001. doi: 10.1088/0953-8984/26/7/076001. Epub 2014 Jan 29.
The transport and magnetic properties (ac linear and nonlinear (second and third orders) susceptibilities) are presented for La0.8Ca0.2MnO3 and La0.8Ca0.2CoO3 single crystals with insulator ground states. The ferromagnetic (FM) clusters with similar magnetic characteristics originate in the paramagnetic phases of both compounds below some temperature T(∗). At high temperatures the FM clusters arise at the preferable sites that can be attributed to the chemical inhomogeneities, their density being weakly T-dependent. On cooling a homogeneous nucleation of the FM clusters develops below a definite temperature T(#) that is characterized by a fast growth of their density. These two stages are observed in both compounds. At the third stage a coalescence of the FM clusters starts in the doped cobaltite, whereas in the manganite the development of matrix FM ordering occurs which changes a cluster's behavior. The indicated features support the common nature of the cluster state in the doped cobaltite and manganite. The difference in their evolution is a consequence of the different magnetic properties of the matrices in the manganite and cobaltite.
本文报道了 La0.8Ca0.2MnO3 和 La0.8Ca0.2CoO3 具有绝缘基态的单晶体的输运和磁性质（交流线性和非线性（二阶和三阶）磁化率）。在低于某个温度 T(∗)时，两种化合物的顺磁相中都存在具有相似磁特性的铁磁（FM）团簇。在高温下，FM 团簇出现在优先位置，这可以归因于化学不均匀性，其密度与温度的关系较弱。在冷却过程中，低于某个确定的温度 T(#)会发生 FM 团簇的均匀成核，此时其密度迅速增长。这两个阶段在两种化合物中都有观察到。在第三阶段，掺杂钴酸盐中的 FM 团簇开始合并，而在锰酸盐中则发生基质 FM 有序化的发展，这改变了团簇的行为。这些特征表明，掺杂钴酸盐和锰酸盐中的团簇态具有共同的性质。它们的演化差异是锰酸盐和钴酸盐中基质磁性质不同的结果。
