The effect of Mn substitution on the structure and magnetic properties of Se(Cu_1−xMn_x)O₃ solid solution

The effects of Mn substitution on the structure and magnetic properties of the SeMO₃ (M = Cu_1−xMn_x) solid solution have been studied. Rietveld refinements of the x-ray diffraction patterns of these samples indicate that the manganese ions occupy copper sites. This replacement induces significant changes in the M–O bond lengths that give rise to abrupt decreases of the [M–O₆] octahedral distortion. In contrast, the M–O(1)–M and M–O(2)–M bond angles remain essentially constant. The magnetic behaviour of this solid solution was studied in the temperature range of 2 K < T < 300 K. The temperature dependence of the inverse magnetic susceptibility is well described by the Curie–Weiss law at high temperatures, in the composition range studied. We found that the substitution of Mn for Cu induces a sharp drop in the saturation moment of SeCuO₃. At about 10% of Mn there is a change from positive to negative Weiss constant θ_W that is mainly due to the [M–O₆] octahedral distortion introduced by the substitution of the larger Mn ions in the structure. The M– H isotherms show a weak ferromagnetism at about 52 K in SeMnO₃.