Phase Relationship and Magnetostriction of Tb–Dy–Ho–Fe Alloys

Abstract

The phase relationship of $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ $(1.6\le x\le 2.4)$ alloys in the Tb–Dy–Ho–Fe system was determined by using optical microscopy, X-ray diffraction, and differential thermal analysis. The vertical section of $\mbox{Tb}_{{\kern-.5pt}0{\kern-.25pt}.{\kern-.25pt}26}\mbox{Dy}_{{\kern-.25pt}0{\kern-.25pt}.{\kern-.25pt}49}\mbox{Ho}_{{\kern-.5pt}0{\kern-.25pt}.{\kern-.25pt}25}\mbox{Fe}_{{\kern-.5pt}x}$ alloys consists of two single-phase regions, namely, L (liquid) and (Tb, Dy, Ho)Fe 2, and four two-phase regions, namely, L + (Tb, Dy, Ho)Fe 3, L + (Tb, Dy, Ho)Fe 2, (Tb, Dy, Ho)Fe 2 + (Tb, Dy, Ho)Fe 3, and (Tb, Dy, Ho)Fe 2 + (Tb, Dy, Ho). The range between the liquidus and peritectic temperatures for $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ alloys becomes narrow with addition of Ho, which is beneficial to decrease the properitectic (Tb, Dy, Ho)Fe 3 phase. The magnetic field dependence of magnetostriction $(\lambda_{//},\lambda_{\perp})$ for $\mbox{Tb}_{0.26}\mbox{Dy}_{0.49}\mbox{Ho}_{0.25}\mbox{Fe}_{x}$ alloys has been determined. The magnetostriction quickly increases with increasing magnetic field value when it is less than 240 kA/m. Among the present studied alloys, the sample with $x=1.9$ possesses the largest magnetostriction. It has been found that magnetic annealing improves the magnetostriction $\lambda_{//}$ of Tb 0.26Dy 0.49Ho 0.25Fe 1.9 alloy.