Charge and spin orders through cascading charge disproportionation transitions in SmBaFe2O6

The recently synthesised A-cation layered double perovskite SmBaFe2O6 containing mixed and unusually high valent Fe3.5+ has been found to show a cascade of charge disproportionation transitions that can be described as 2Fe3.5+ → Fe3+ + Fe4+ → 1.5Fe3+ + 0.5Fe5+ on cooling. While the first charge transition is accompanied by structural and magnetic transitions, the second transition occurs gradually with successive magnetic anomalies and significant temperature and magnetic field hysteresis. To reveal the charge orders and magnetic structures, we propose temperature-dependent neutron diffraction experiments at the WISH diffractometer. The expected results will provide new insights into unusual phase transition phenomena of transition-metal oxides with strong correlation of charge, spin, and lattice degrees of freedom.

近期合成的A位阳离子层状双钙钛矿（A-cation layered double perovskite）SmBaFe2O6，其包含混合价态且异常高价的Fe3.5+，在降温过程中呈现出一系列电荷歧化转变（charge disproportionation transitions），该转变过程可描述为2Fe3.5+ → Fe3+ + Fe4+ → 1.5Fe3+ + 0.5Fe5+。首次电荷转变同时伴随结构与磁相变（structural and magnetic transitions），而第二次转变则逐渐发生，伴随连续的磁异常（magnetic anomalies）以及显著的温度与磁场磁滞（temperature and magnetic field hysteresis）。为揭示其电荷序（charge orders）与磁结构（magnetic structures），我们提议在WISH衍射仪（WISH diffractometer）上开展变温中子衍射实验（temperature-dependent neutron diffraction experiments）。预期的实验结果将为理解电荷、自旋与晶格自由度（charge, spin, and lattice degrees of freedom）强关联的过渡金属氧化物（transition-metal oxides）的非常规相变现象提供新的见解。