Estimation of second order phase transition temperature of the orthorhombic phase of Gd5(SixGe1-x)4 using Arrott plots

Abstract

Gd5 (Six Ge1-x)4 for 0.41≤x≤0.5 is orthorhombic and ferromagnetic at lower temperature, monoclinic and paramagnetic at higher temperature, and shows a first order magnetic-structural phase transition between the two. Magnetic moment versus magnetic field (MH) isotherms were measured just above the first order transition temperature for Gd5 Si1.95 Ge2.05 and Gd5 Si2 Ge2 samples and the field-induced coupled phase transition from paramagnetic/monoclinic to ferromagnetic/orthorhombic phase was observed. Using the method developed by Arrott [Phys. Rev. 108, 1394 (1957)], the ferromagnetic portions of the MH isotherms were used to project the second order magnetic phase transition temperature of the orthorhombic phase, a region where the transition does not occur due to the first order transition at a lower temperature. These data points fall on the extrapolated line of the second order phase transition, drawn from the Si-rich region of the phase diagram. © 2008 American Institute of Physics.