Temperature dependence of magnetostriction of Gd/Tb alloys

Abstract

The aim of the present study was to understand the mechanism responsible for the exceptionally high magnetostriction exhibited by the heavy rare earths. Magnetostriction constants λ(^ɤ,2),λ(^ɑ,2) and λ(_1)(^ɑ,2) of order ȴ = 2 for gadolinium, terbium and their alloys were measured using a resistive strain gauge technique. The temperature dependence of these magnetostriction constants was observed from liquid helium temperature to close to their Curie temperatures for Gd, 90%Gd-10%Tb, 70%Gd-30%Tb, 507oGd-50%Tb, 10%Gd-90%Tb and Tb. The adequacy of theoretical predictions of the temperature dependence was tested with the results of these measurements. The observed temperature dependence of λ(^ɤ,2) over the entire range of temperature and alloy compositions except for pure Gd, was found to follow closely the variation predicted by a theory termed as a single-ion model. The same conclusion resulted from the measurements of λ(_2)(^ɑ,2) and λ(_1)(^ɑ,2) but with less reliability. The extrapolated values of the constants at OK for Gd and its experimental temperature dependence are consistent with results of other investigations on gadolinium. The magnetostriction constants of the alloys varied linearly with the terbium concentration, again showing that the single-ion magnetocrystalline interaction is principally responsible for the magnetostrictive effects due to terbium ions. Some suggestions are included for improvements to experimental and analytical techniques and for the extension to other alloy systems.