Field induced structural phase transition at temperatures above the Curie point in Gd_5(Si_xGe_(1-x))_4

摘要

Gd_5(Si_xGe_(1-x))_4 exhibits a field induced first order phase transition from a monoclinic paramagnetic to an orthorhombic ferromagnetic at temperatures above its Curie temperature for 0.41 ≤ x ≤ 0.51. The field required to induce the transition increases with temperature. This field induced first order phase transition was observed even above the projected second order phase transition temperature of the orthorhombic phase. This may be due to the fact that the applied magnetic field is so high that it causes the broadening to a wider range of higher temperatures of the second order phase transition of the orthorhombic phase, and at such high magnetic fields the magnetic moment is still quite large, therefore, causing the transition. This hypothesis seems to be confirmed by the various magnetic moment versus magnetic field, magnetic moment versus temperature, and strain versus magnetic field measurements carried out on single crystal Gd_5Si_(1.95)Ge_(2.05) and Gd_5Si_2Ge_2 samples at magnetic fields of 0-9 T and at temperatures of 265-305 K.