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首页> 外文期刊>Physical review. B, Condensed Matter And Materials Physics >Metastable diamagnetic response of 20 nm La_(1-x)MnO_3 particles
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Metastable diamagnetic response of 20 nm La_(1-x)MnO_3 particles

机译：20 nm La_（1-x）MnO_3粒子的亚稳态抗磁响应

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摘要

The magnetic properties of compacted 20 nm La_(1-x)MnO_3 particles, prepared by the citrate method, in pristine and metastable states have been investigated. It was found that in its pristine state the investigated sample displays a paramagnetic-to-ferromagnetic transition near T_c≈220 K, below which the relative volume of the ferromagnetic (FM) phase at 5 K approaches a value of about 24%. Magnetization and ac-susceptibility measurements exhibit a cluster-glass-like behavior characterized by a noticeable difference between zero-field-cooled and field-cooled magnetization and frequency-dependent ac susceptibility. Different metastable states with highly reduced FM phase and "negative ferromagnetism" developed after a series of quick coolings of the sample placed in a container filled with silicon oil. The recorded temperature dependence of the negative FM moment appears to be a normalized replica of the corresponding FM dependence. Hysteresis loops of magnetization at low temperatures in both pristine and diamagnetic (DIA) states exhibit the same value of coercive field at 5 K, H_c ≈ 400 Oe. The abnormal DIA state can only be erased after a few hours storage of the sample at room temperature. These observations are discussed with reference to a model in which the negative ferromagnetism is attributed to the appearance of nondispersive orbital currents which result in a coupling between the core of the FM particles and the surrounding diamagnetic matrix formed during the quick cooling cycles.
机译：研究了柠檬酸盐法制备的压实的20 nm La_（1-x）MnO_3颗粒在原始和亚稳态下的磁性。发现在原始状态下，所研究的样品在T_c≈220K附近表现出顺磁至铁磁跃迁，低于5K时铁磁（FM）相的相对体积接近约24％的值。磁化和交流磁化率测量显示出类玻璃状的行为，其特征在于零磁场冷却和磁场冷却的磁化强度与频率相关的交流磁化率之间存在明显差异。在将一系列快速冷却后的样品放入装有硅油的容器中后，出现了具有大大降低的FM相和“负铁磁性”的不同亚稳态。记录的负FM矩的温度依赖性似乎是相应FM依赖性的归一化副本。在原始和反磁性（DIA）状态下，低温下的磁化磁滞回线在5 K，H_c≈400 Oe时显示相同的矫顽场值。只有在室温下保存几个小时后才能消除异常DIA状态。这些观察是参考一个模型讨论的，在该模型中，负铁磁性归因于非弥散性轨道电流的出现，这会导致FM粒子的核心与快速冷却循环中形成的周围抗磁性基质之间的耦合。

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