The spontaneous exchange bias (SEB) effect is a remarkable phenomenon recently observed in some reentrant spin-glass materials. Here we investigate the SEB in La$_{1.5}$(Sr$_{0.5-x}$Ba$_{x}$)CoMnO$_{6}$ double-perovskites, a system with multifarious magnetic phases for which a notable increase in the exchange bias field is observed for intermediate Sr/Ba concentrations. The Ba to Sr substitution leads to the enhancement of the crystal lattice, which is accompanied by the raise of both the effective magnetic moment ($\mu_{eff}$) and the antiferromagnetic (AFM) transition temperature that is observed below the ferromagnetic ordering. Such increases are likely related to the increased fraction of Co$^{3+}$ in the high spin configuration, leading to the enhancement of Co$^{3+}$--O--Mn$^{4+}$ AFM phase and to the reduction in the uncompensation of the AFM coupling between Co and Mn. The combined effect of the increased $\mu_{eff}$ and AFM phase plausible explains the changes in the SEB effect.

中文翻译：

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在 La1.5(Sr0.5−xBax)CoMnO6 中调节 Ba 到 Sr 部分取代的自发交换偏置效应

自发交换偏置 (SEB) 效应是最近在一些重入自旋玻璃材料中观察到的显着现象。在这里，我们研究了 La$_{1.5}$(Sr$_{0.5-x}$Ba$_{x}$)CoMnO$_{6}$ 双钙钛矿中的 SEB，这是一个具有多种磁相的系统对于中等 Sr/Ba 浓度，观察到交换偏置场的显着增加。Ba 到 Sr 的取代导致晶格的增强，伴随着有效磁矩 ($\mu_{eff}$) 和反铁磁 (AFM) 转变温度的升高，在铁磁有序之下观察到. 这种增加可能与高自旋配置中 Co$^{3+}$ 的比例增加有关，导致 Co$^{3+}$--O--Mn$^{4+}$ AFM 相的增强，并减少 Co 和 Mn 之间的 AFM 耦合的未补偿。增加的 $\mu_{eff}$ 和 AFM 相位的组合效应解释了 SEB 效应的变化。