Magnetic and mössbauer studies of CaRu_1-xM_xO₃ (M=Ti and Fe)

CaRuO₃ is a perovskite with an orthorhombic distortion and shows the characteristics of spin-glass behavior below T_C=87 K. Magnetic studies of polycrystalline CaRu_1-xTi_xO₃ (0<x<0.1) reveal that a ferromagnetic transition at Tc=34 K appears regardless of the nonmagnetic Ti concentration. On the other hand, magnetic and Mössbauer effect studies show that T_C of CaRu_1-xFe_xO₃ (up to x=0.15) is similar to that of pure CaRuO₃: however, the Fe induces a ferromagnetic structure. Charge compensation, which is assumed to be present upon Fe³⁺ substitution, induces the appearance of low-spin Ru⁵⁺ ions, which reduce the paramagnetic moment. Huge magnetic hysteresis loops are observed at 5 K, with coercive fields up to 30 kOe. A second magnetic transition around 250 K is observed for Fe concentrations of x=0.25 and 0.35, which is probably caused by Fe-rich clusters. This behavior is consistent with inhomogeneous ferromagnetism found in other perovskite systems.