Spin reorientation and magnetoelastic properties of ferromagnetic T b1-x N dx C o2 systems with a morphotropic phase boundary

The spin reorientation (SR) and magnetoelastic properties of pseudobinary ferromagnetic Tb1-xNdxCo2 (0≤x≤1.0) systems involving a morphotropic phase boundary (MPB) were studied by high-resolution synchrotron x-ray diffraction (XRD), magnetization, and magnetostriction measurements. The easy magnetization direction of the Laves phase lies along the (111) axis with x<0.65, whereas it lies along the (100) axis for x>0.65 below Curie temperature (TC). The temperature-dependent magnetization curves showed SR; this can be explained by a two-sublattice model. Based on the synchrotron (XRD) and magnetization measurements, the SR phase diagram for a MPB composition of Tb0.35Nd0.65Co2 was obtained. Contrary to previously reported ferromagnetic systems involving MPB, the MPB composition of Tb0.35Nd0.65Co2 exhibits a low saturation magnetization (MS), indicating a compensation of the Tb and Nd magnetic moments at MPB. The anisotropic magnetostriction (λS) first decreased until x=0.8 and then continuously increased in the negative direction with further increase of Nd concentration. The decrease in magnetostriction can be attributed to the decrease of spontaneous magnetostriction λ111 and increase of λ100 with opposite sign to λ111. This paper indicates an anomalous type of MPB in the ferromagnetic Tb1-xNdxCo2 system and provides an active way to design novel functional materials with exotic properties.