Synthesis and Magnetic Properties of Rare Earth-Alkaline Metal M-Type Ferrites

Abstract

The apparent phases and magnetic properties of ferrites of the RE₂O₃-AM₂O-Fe₂O₃ system (RE=Y, La, Ce, Pr, Nd, Sm, Gd, and AM=Na, K, Rb) were studied. The observed phases were classified according to the combination of rare earth metal and alkaline metal. M-type ferrites, which have a magnetoplumbite structure, were obtained in the La₂O₃AM₂O-Fe₂O₃system (AM=Na, K, Rb). M-type ferrites were synthesized at over 1473 K for the La-Na system, 1573 K for the La-K system, and 1673 K for the La-Rb system. A single phase of M-type ferrite was prepared in (La_1-xK_x)O·6Fe ₂O₃ at x=0.2. The magnetization of (La_0.8K_0.2)O·6Fe₂O₃ is 86μWb·m·kg^-1,and the Curie temperature is 708 K.