Some Crystallographic and Magnetic Properties of Square-Loop Materials in Ferrite Systems Containing Copper

Abstract

Rectangular hysteresis loops have been found in ferrite systems containing copper during an investigation based on the proposal by Baltzer that a zero or near-zero value of the effective magnetocrystalline domain anisotropy is a necessary condition for loop squareness. Data on hysteresis loop squareness of polycrystalline bodies as a function of composition, firing conditions and magnetostrictive effects are presented for the system: copper ferrite-magnesium ferrite. This system is characterized in general by large grains and long switching times. Abrupt flux changes occur in the hysteresis loop at low temperatures. Simultaneously, a decrease in the coercive force with decreasing temperature and squareness values approaching unity are observed. No crystallographic transitions were detected at low temperatures. Magnetostrictive measurements do not unequivocally show whether anisotropy goes through zero at compositional region of maximum squareness. The saturation magnetostriction and probably the λ111 go through a minimum in this region.