Magnetostriction of dilute metallic rare earth alloys: LaSb: Dy and Ag:R (R= Tb, Dy, Ho, Tm)

We present a method to analyze the magnetostriction of dilute rare earth alloys. It consists of a calculation of the free-energy using the complete "single ion" Hamiltonian. Our calculation nicely fits the magnetostriction data on Ag : R alloys measured by Creuzet and Campbell along the [001] direction without the need to introduce the fourth order term. The theory is also used, to analyze our magnetostriction results of LaSb: By single crystals along the [001] direction. The fitting procedure yields a second order magnetoelastic coupling constant of V(Γ₃) = + 19.3K/ion which is slightly smaller than the value V(Γ₃) = + 24K/ion found by Bloch and Davidov from magnetization measurements on LaSb : Dy. The difference, we believe, is due to the face that magnetization reflects the local microscopic distortion as seen by the rare-earth ion while magnetostriction measures the macroscopic "long range" distortion away from the rare-earth ions.