Zhao Z Y, Che H L, Chen R, Wang J F, Sun X F, He Z Z
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China.
J Phys Condens Matter. 2019 Jul 10;31(27):275801. doi: 10.1088/1361-648X/ab1623. Epub 2019 Apr 4.
Magnetism of Cu(OH)Br single crystals based on a triangular lattice is studied by means of magnetic susceptibility, pulsed-field magnetization, and specific heat measurements. There are two inequivalent Cu sites in an asymmetric unit. Both Cu sublattices undergo a long-range antiferromagnetic (AFM) order at [Formula: see text] K. Upon cooling, an anisotropy crossover from Heisenberg to XY behavior is observed below 7.5 K from the anisotropic magnetic susceptibility. The magnetic field applied within the XY plane induces a spin-flop transition of Cu ions between 4.9 T and 5.3 T. With further increasing fields, the magnetic moment is gradually increased but is only about half of the saturation of a Cu ion even in 30 T. The individual reorientation of the inequivalent Cu spins under field is proposed to account for the magnetization behavior. The observed spin-flop transition is likely related to one Cu site, and the AFM coupling among the rest Cu spins is so strong that the 30 T field cannot overcome the anisotropy. The temperature dependence of the magnetic specific heat, which is well described by a sum of two gapped AFM contributions, is a further support for the proposed scenario.
通过磁化率、脉冲场磁化和比热测量研究了基于三角晶格的Cu(OH)Br单晶的磁性。在一个不对称单元中有两个不等价的铜位点。两个铜亚晶格在[公式：见正文]K时经历长程反铁磁（AFM）有序。冷却时，从各向异性磁化率可观察到在7.5K以下从海森堡行为到XY行为的各向异性转变。在XY平面内施加的磁场在4.9T和5.3T之间诱导铜离子的自旋翻转转变。随着磁场进一步增加，磁矩逐渐增加，但即使在30T时也仅约为铜离子饱和值的一半。提出不等价铜自旋在磁场下的单独重取向来解释磁化行为。观察到的自旋翻转转变可能与一个铜位点有关，其余铜自旋之间的AFM耦合非常强，以至于30T的磁场无法克服各向异性。磁性比热的温度依赖性由两个有能隙的AFM贡献之和很好地描述，这进一步支持了所提出的情景。
