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 GdGa 1− x Al x 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 GdGa 1− x Al x (0 ≤ x ≤ 0.3) compounds were measured by X-ray diffraction (XRD) analysis. The crystal structure of GdGa 1− x Al x 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 GdGa 1− x Al x 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 GdGa 1− x Al x 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 (− ∆ S M ) for the GdGa 1− x Al x 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 GdGa 1− x Al x .