Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Phys Rev Lett. 2023 May 5;130(18):186801. doi: 10.1103/PhysRevLett.130.186801.
Perovskite rare earth nickelates exhibit remarkably rich physics in their metal-insulator and antiferromagnetic transitions, and there has been a long-standing debate on whether their magnetic structures are collinear or noncollinear. Through symmetry consideration based on the Landau theory, we discover that the antiferromagnetic transitions on the two nonequivalent Ni sublattices occur separately at different Néel temperatures induced by the O breathing mode. It is manifested by two kinks on the temperature-dependent magnetic susceptibilities with the secondary kink being continuous in the collinear magnetic structure but discontinuous in the noncollinear one. The prediction on the secondary discontinuous kink is corroborated by an existing magnetic susceptibility measurement on bulk single-crystalline nickelates, thus strongly supporting the noncollinear nature of the magnetic structure in bulk nickelates, thereby shedding new light on the long-standing debate.
钙钛矿结构的稀土镍酸盐在金属-绝缘体和反铁磁转变中表现出丰富的物理性质，其磁结构是共线还是非共线一直存在争议。通过基于朗道理论的对称性考虑，我们发现两个不等价的 Ni 亚晶格上的反铁磁转变分别在由 O 呼吸模式引起的不同奈尔温度下发生。这表现为在温度依赖的磁化率上有两个拐点，其中第二个拐点在共线磁结构中是连续的，但在非共线磁结构中是不连续的。关于第二个不连续拐点的预测得到了块状单晶镍酸盐的现有磁化率测量的证实，从而强烈支持了块状镍酸盐中磁结构的非共线性质，从而为这一长期存在的争议提供了新的视角。
