Magnetomechanical coupling and ΔE effect in highly magnetostrictive rare earth - Fe<inf>2</inf>compounds

Abstract

We have measured the magnetomechanical coupling in highly magnetostrictive Tb x Dy 1-x Fe 2-δ as a function of bias field, x, and δ. We find a peak coupling factor of 0.6 at x = .26 and bias field of 180 Oe; the largest reported for a magnetostrictive material. The corresponding material Q is 200. Because of the high magnetostriction, relative permeabilities are necessarily low; \mu_{\max} \simeq 5 . Young's modulus at constant field changes from 4.5 to ll (x1010n/m2) as the bias changes from zero to 4.5 kOe, corresponding to a change in sound velocity >50%. The magnetomechanical coupling factor was also evaluated for 0 \leq \delta \leq .3 . When δ is non-zero a eutectic second phase is present which acts as a toughening agent.