MAGNETIC-PROPERTIES OF A0.6 PB0.4 MNO3 PEROVSKITES (A=ND, SM, GD)

Crystal structure and magnetic properties of A0,6Pb0,4MnO3 perovskite is found to be a ferromagnetic material (T(c) = 180 K). The compound unit cell is distorted rhombohedrally. The Sm perovskite is distinguished by a O1-orthorhombic distortion of the unit cell and is an inhomogeneous ferromagnet below 90 K. The O1-orthorhombic distortion is inherent also in the Gd perovskite unit cell. Below 40 K one can observe magnetic properties typical of spin glasses. Transition to a <<frozen>> state is realized by locking gradually the magnetic moments of the ferromagnetic clusters. As the REI radius decreases, the perovskite crystal structure is distorted because of mismatch between ionic radii of REI and manganese. The Jahn - Teller dynamic effect becomes static, promoting a change in the mechanism of exchange interactions.