Magnetic and Structural Studies on Two-Dimensional Antiferromagnets (MCl)LaNb^sub 2^O^sub 7^ (M = Mn, Co, Cr)

• Published in: Journal of the Physical Society of Japan 2016-03, Vol.85 (3), p.1
• Main Authors: Kitada, Atsushi, Tsujimoto, Yoshihiro, Nishi, Masakazu, Matsuo, Akira, Kindo, Koichi, Ueda, Yutaka, Ajiro, Yoshitami, Kageyama, Hiroshi
• Format: Article
• Language: English
• Subjects: Electrons; Magnetic fields; Perovskite; Phase transitions
• ISSN: 0031-9015; 1347-4073

We report magnetic and structural studies on the two-dimensional antiferromagnets (MCl)LaNb...O... (M = Mn, Cr, Co), prepared by topochemical reactions of a layered perovskite RbLaNb...O... Electron diffraction of these oxyhalides revealed a superstructure with a ...a x ...a cell for M = Mn and Co, and a 2a x 2a cell for M = Cr, indicating that the MCl networks are distorted from an ideal square lattice. Neutron diffraction experiments showed that M = Mn and Co exhibit a (... 0 ...) antiferromagnetic order as observed for the S = 1/2 counterparts. (CoCl)LaNb...O... with a strong spin anisotropy shows an antiferro to weak-ferromagnetic transition at low field, followed by novel two-step metamagnetic transitions likely associated with a 1/2 plateau for 27-54 T. Possible spin structures under magnetic field are discussed in terms of an Ising-type model. By contrast, (CrCl)LaNb...O... exhibits a (... ... ...) order, which is the first observation among related oxyhalides, and a spin-flop transition at 12 T due to a weak spin anisotropy. These results suggest that a slight difference in the MCl structure and spin anisotropy provides a crucial influence on the magnetic properties. (ProQuest: ... denotes formulae/symbols omitted.)