$Sr_4M_3ReO_{12}$ (M = Co, Fe): New Ferromagnetic Perovskite Oxides

Abstract

We describe the synthesis, structure, and magnetic properties of two new perovskite oxides, $Sr_4M_3ReO_{12}$ (M =Co, Fe), that exhibit ferromagnetism with fairly high ordering temperatures $(T_c = \sim 250-300 K)$. While the M = Co phase crystallizes in a partially ordered double perovskite $(Pm\={3}m)$ structure (a = $7.8153 \AA$), the M = Fe phase adopts a primitive cubic perovskite $(Pm\={3}m)$ structure (a = $3.9353 \AA$), where the transition metal atoms are not ordered in the long range. Magnetization studies revealed bulk ferromagnetism for both oxides, but the disordered structures seem to preclude a long-range magnetic order and a definite $T_c$. While further studies are needed to establish the exact origin of magnetism of these materials, the present investigation reveals the possibility of designing new ferromagnetic oxides based on $M^{3+}-O-Re^{7+}$ (M =Co, Fe) magnetic interaction in the perovskite related structures