Magnetic structure of random magnetic mixtures with competing Anisotropy-CsMn1-xCoxCl3.2H2O

Magnetic structures and phase transitions of CsMn 1- x Co x Cl 3 ·2H 2 O, a typical substance of random magnetic mixtures with competing magnetic anisotropy, are investigated theoretically by assuming a simplified model: classical 2-D X - Y model with the single-ion type anisotropy. The magnetic susceptibility for each easy axis and the thermal average of each spin are calculated by Monte-Carlo simulation. It results that the characteristic features of the phase diagram are reproduced, that is, besides the CsMnCl 3 ·2H 2 O-type antiferromagnetic phase and the CsCoCl 3 ·2H 2 O-type one, an intermediate phase exists in between the two phases. In the intermediate region, two successive phase transitions occur with increasing temperature. It is found that the spin structure of the intermediate phase has two perpendicular antiferromagnetic domains linked by domain walls. This result is consistent with the NMR experiments.