Critical behavior in the perovskite-like system Y(Ni,Mn)O3

The electrical and magnetic properties of the perovskite-type solid solution YNixMn1−xO3 have been studied at different temperatures and magnetic fields. Electrical conductivity measurements have shown a semiconductor behavior throughout the solid solution. The room temperature conductivity increases with the Ni concentration until x=1/3, and then decreases for higher Ni contents. The effective moment in the paramagnetic state shows a clear break at x=xcrit=1/3, presenting a constant value at x≤xcrit and decreasing at higher nickel concentration. In the ordered state, other magnetic parameters show similar discontinuities versus the nickel content, such as a sudden increase of the magnetization at high field or a maximum in the coercive strength of the ferromagnetic-like M(H) loop. By charge-conservation arguments we can readily identify such critical value as an optimum conversion of Mn3+ into Mn4+, leading to the charge-balance formula Y3+[Ni1/32+(Mn3+0.5Mn4+0.5)2/3]O32−, that is, equal amounts of Mn3+ and Mn4+ in the sample. Magnetic data shows that, at x≤xcrit, the solid solution behaves as a spin-glass and/or antiferromagnetic system, while at x>xcrit, full ferromagnetic characteristics are observed.