Temperature dependent magnetization and coercivity in morphotropic phase boundary involved ferromagnetic Tb1-xGdxFe2 system

Abstract

Morphotropic phase boundary (MPB) refers to a transition region separating two ferromagnetic phases having different crystallographic symmetries in a ferromagnetic system. In the present study, magnetization and coercivity of the MPB involved ferromagnetic Tb1-xGdxFe2 system have been measured at selected temperatures between 5 and 300 K. The saturation magnetization MS of the Tb1-xGdxFe2 system varies with Gd concentration exhibiting minimum value at MPB composition x = 0.9 at all temperatures. Calculated magnetic moments of rare earth (RE) elements are lower than those of their corresponding free ions, which can be attributed to the crystal field effect (CFE). The magnetic anisotropy K decreases with increasing Gd concentration and anisotropy compensation has been observed at an MPB composition with x = 0.9. The coercivity HC of the Tb1-xGdxFe2 system was found to decrease with increasing the Gd concentration. Furthermore, HC exhibits a large value at low temperature and decays exponentially with increasing temperature. The observed temperature dependence of the HC can be explained by domain wall pinning, as a high K of rare earth elements (RE) at low temperatures causes a prominent pinning effect at 5 K. Our results shed light on magnetization, magnetic anisotropy and coercivity mechanisms in MPB involved ferromagnetic systems and provides an effective way to design novel functional materials.