The effect of Al on crystal structure and magnetic properties of GdGa

In the family of Rare earth gallium (RGa) compounds, GdGa is rich in magnetic phase transitions and offers a great range for phase transition modulation and optimization of magnetic entropy transition properties. The GdGa1-xAlx compounds were prepared via a vacuum arc melting method to investigate the effect of Al on the GdGa compound. The crystal structure and phase analysis on the GdGa1-xAlx (0 <= x <= 0.3) compounds were measured by X-ray diffraction (XRD) analysis. The crystal structure of GdGa1-xAlx belongs to an orthorhombic CrB type with the space group of Cmcm. The results of Rietveld refinement show that the lattice parameters a, b, c, and volume V are all enlarged with the increasing Al content. The magnetic measurement by Vibrating Sample Magnetometer (VSM) found that the GdGa1-xAlx compounds underwent two magnetic transitions, i.e., spin reorientation (SR) and ferromagnetic to paramagnetic (FM-PM) transition when increasing temperature. As the content of Al increases from 0.1 to 0.3, the transition temperature of spin reorientation (T-SR) of the GdGa1-xAlx compounds raised from 105 to 142 K, and the FM-PM transition temperature (T-C) decreased from 183 to 176 K. The maximum value of magnetic entropy change (- increment S-M) for the GdGa1-xAlx compounds under an applied magnetic field of 1.5 T are 2.41, 2.44, 2.51, and 2.60 J kg(-1) K-1, respectively. The respective refrigeration capacities (RC) are 106.1, 107.5, 110.6, and 119.5 J kg(-1), with increases along GdGa1-xAlx.