Magnetostriction and Anomalous Thermal Expansion of Single Crystals of Gadolinium

Measurements have been made with strain gauges of the magnetostriction, λ, and the thermal expansion coefficient, α, of gadolinium single crystals from 4°K to above the Curie point. The four magnetostriction constants appropriate for a hexagonal crystal have been evaluated, and special attention has been given to the forced magnetostriction and its relation to the anomalous thermal expansion near the Curie point. By the use of the usual thermodynamic relations the results show that compressive stress when applied parallel to the hexagonal c axis reduces the molecular field, as in iron, and when applied parallel to the a axis it increases the molecular field, as in nickel. The anomaly in the thermal contraction is unusually large in the c direction. Both λ and α were also measured for polycrystalline material.