Elastic moduli of some ferrites at low temperatures

Abstract

Elastic moduli of nickel-zinc (two different compositions), manganese—zinc and barium ferrites were determined as a function of temperature from 80 to 303 K. The experimental method employed was the composite piezo-electric oscillator capable of measuring elastic wave velocities to a few parts in 10⁴. The elastic moduli of nickel-zinc ferrites were found to increase with decrease in temperature almost linearly whereas in barium ferrite, the moduli decrease with decreasing temperature showing some sort of hysteresis effect. However, in the case of manganese-zinc ferrite the elastic moduli first decrease with decrease in temperature to about 257 K and from there onwards increase with further decrease in temperature down to the boiling point of liquid air (80 K). The existence of a dip in the moduli versus temperature curves of manganese-zinc ferrite was suspected to be due to stress-induced relaxation at grain boundaries.