LaMn1-xFexO3 +y系统的磁相演化
Magnetic phases evolution in the LaMn1-xFexO3+y system
摘要：
研究了在空气中固相反应制备的LaMn_（1-x）Fe_xO_（3 +y）多晶样品的晶体结构和磁性。所有样品均显示ORT-2正交结构，其抑制了Jahn-Teller畸变，从而有利于Mn^{3+}-O-Mn^{3+}之间的铁磁（FM）超交换（SE）相互作用。当x=0.0时，氧过量（y ~ 0.09）在La和Mn位产生空位，并产生约18%的Mn^{4+}离子和82%的通常Mn^{3+}离子，它们之间可能存在双交换作用。已知该体系中的Fe掺杂仅产生稳定的Fe^{3+}离子。我们发现从一个相当强的FM相的居里温度T_{C} ~ 160 K，x=0.0，反铁磁（AFM）相T_{N} = 790 K，x=1.0，伴随着明确的签名的集群玻璃行为的演变。对于中间Fe含量，发生混合相状态，FM（AFM）相逐渐减少（增加），伴随着0.2 < x < 0.7的系统转变加宽。一个模型的基础上预期的各种磁性离子类型之间的交换相互作用，占很好的饱和磁化依赖于Fe掺杂。
英文摘要：
We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange (SE) interaction between Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82% of the usual Mn^{3+} ions, with possible double exchange interaction between them. The Fe doping in this system is known to produce only stable Fe^{3+} ions. We find an evolution from a fairly strong FM phase with a Curie temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2 < x < 0.7. A model based on the expected exchange interaction among the various magnetic-ion types, accounts very well for the saturation-magnetization dependence on Fe doping.
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