NEUTRON-DIFFRACTION STUDY OF THE MAGNETIC-ORDERING IN THE INSULATING REGIME OF THE PEROVSKITES RNIO3 (R=PR AND ND)
NEUTRON-DIFFRACTION STUDY OF THE MAGNETIC-ORDERING IN THE INSULATING REGIME OF THE PEROVSKITES RNIO3 (R=PR AND ND)
复制标题
DOI：
10.1103/physrevb.50.978
复制
发表时间：
1994-07-01
影响因子：
3.7
通讯作者：
LACORRE, P
中科院分区：
文献类型：
--
作者：
GARCIAMUNOZ, JL;RODRIGUEZCARVAJAL, J;LACORRE, P
中子衍射实验和极化分析技术表明，在正交钙钛矿PrNiO3和NdNiO3中，金属-绝缘体转变伴随着Ni位的突然三维磁有序（mu（Ni）几乎等于0.9mu(B)）。电子定位之后是一个磁基态，由一个不寻常的反铁磁结构组成，相对于正交晶胞，k =(1/2, 0,1 /2)。这个传播矢量意味着沿三个伪轴的铁磁和反铁磁耦合对称共存。这表明存在单个e(g)电子的非均匀轨道分布。轨道超晶格可能是Ni(III)（t2g6e(g)1）态简并态因电子相关而被击穿的结果。这种自旋排列在其他钙钛矿氧化物中尚未观察到。这些发现被单晶Nd位的磁性行为所证实：在一个简单的顺磁体中，这些离子的一半变得有序，另一半保持无序。这可以解释为由镍矩交换场引起的极化效应和Ni位点点对称的破坏。
Neutron-diffraction experiments and polarization analysis techniques reveal that the metal-insulator transition in the orthorhombic perovskites PrNiO3 and NdNiO3 is accompanied by a sudden three-dimensional magnetic ordering of the Ni sites (mu(Ni) almost-equal-to 0.9mu(B)). The electronic localization is followed by a magnetic ground state consisting of an unusual antiferromagnetic structure, with k = (1/2 , 0, 1/2) relative to the orthorhombic crystal cell. This propagation vector implies the symmetrical coexistence of ferro- and antiferromagnetic couplings along the three pseudocubic axes. This suggests the existence of a nonuniform orbital distribution of the single e(g) electron. The orbital superlattice may result from the breakdown of the degeneracy of the Ni(III)(t2g6e(g)1) state due to electronic correlation. This type of spin arrangement has not been observed in other perovskite oxides. These findings are confirmed by the magnetic behavior of the single crystallographic Nd site: half of these ions become ordered and the other half remain disordered as in a simple paramagnet. This can be explained by the combination of polarization effects due to the exchange field from nickel moments and the breaking down of point symmetry at Ni site.