Magnetic structure of random magnetic mixtures with competing anisotropy-CsMn1-xCoxCl3.2H(2)O

Magnetic structures and phase transitions of CsMn1-xCoxCl3. 2H(2)O, a typic al 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 susceptibil ity for each easy axis and the thermal average of each spin are calculated by Monte-Carlo simulation. It results that the characteristic features of t he phase diagram are reproduced: that is, besides the CsMnCl3. 2H(2)O-type antiferromagnetic phase and the CsCoCl3. 2H(2)O-type one, an intermediate p hase exists in between the two phases. In the intermediate region, two succ essive phase transitions occur with increasing temperature. It is found tha t the spin structure of the intermediate phase has two perpendicular antife rromagnetic domains linked by domain walls. This result is consistent with the NMR experiments.