Laboratory for Neutron Scattering, Paul Scherrer Institut, Villigen PSI, Switzerland.
J Phys Condens Matter. 2010 Oct 27;22(42):426001. doi: 10.1088/0953-8984/22/42/426001. Epub 2010 Oct 4.
In continuation of our recent x-ray study of the structural phase transitions in the AFeO(2) (A = K, Rb, Cs) family, we have systematically investigated the respective structural and magnetic phase transitions by neutron powder diffraction. While the temperatures of the first-order structural phase transitions are strongly different for the three compounds (~1003, ~737 and ~350 K for A = K, Rb, Cs) and systematically decrease with increasing ionic radius of the A-cation, the magnetic transition temperatures in all three compounds have been found to be almost the same-slightly above 1000 K. The magnetic ordering type is similar in all three compounds-antiferromagnetic ordering of magnetic Fe(3 + ) ions within the system of the three-dimensional Fe-O-Fe linkages such that the Fe-Fe exchange between the nearest neighboring ions is always antiferromagnetic. The directions of magnetic Fe moments were found to be parallel to the crystallographic axis c in RbFeO(2) and CsFeO(2) and parallel to the axis b in KFeO(2) in notations of their low-temperature orthorhombic modifications.
继我们最近对 AFeO(2)（A = K、Rb、Cs）系列结构相变的 X 射线研究之后，我们通过中子粉末衍射系统地研究了各自的结构和磁相变。虽然三种化合物的一级结构相变温度差异很大（1003、737 和~350 K，对于 A = K、Rb、Cs），且随 A-阳离子离子半径的增大而系统降低，但在所有三种化合物中发现磁转变温度几乎相同-略高于 1000 K。三种化合物中的磁性有序类型相似-磁性 Fe(3+)离子在三维 Fe-O-Fe 键系中的反铁磁有序，使得最近邻离子之间的 Fe-Fe 交换始终为反铁磁。在低温正交相变体的标记中，发现磁 Fe 矩的方向在 RbFeO(2)和 CsFeO(2)中平行于晶轴 c，在 KFeO(2)中平行于轴 b。
