Magnetoelasticity in SmFe2

Abstract

The temperature and magnetic field dependence of the elastic moduli of Sm${\mathrm{Fe}}_2$ Laves phase compound has been investigated by means of an ultrasonic-pulse technique at a frequency of 10 MHz. The spin reorientation from the high-temperature easy direction of magnetization [111] to the low-temperature easy axis directed along [110], was observed to occur at $T_{sr}=195\mathrm{}$ °K. The behavior of the elastic moduli near $T_{sr}$ suggests a first-order phase change. Applied magnetic fields strongly affect the temperature dependence and the absolute values of the elastic moduli of Sm${\mathrm{Fe}}_2$. The elastic moduli increase significantly with increased magnetic fields, yielding a low and temperature-independent adiabatic compressibility. A remarkably high (42%) $\Delta E$ effect was observed in Sm${\mathrm{Fe}}_2$ at room temperature, 10-MHz ultrasonic frequency, and an applied magnetic field of 25 kOe. The magnetostriction of Sm${\mathrm{Fe}}_2$ is high and negative. For a field of 25 kOe at room temperature and 77 °K values are -2100 × ${10}^{-6\mathrm{}}$ and -3340 × ${10}^{-6\mathrm{}}$, respectively. The limiting value of the Debye temperatures were found to be 200 and 212 °K, for the unmagnetized and at 25 kOe, respectively.