Magnetic properties of metastable Gd–Cr alloys

We report on the magnetization, magnetocaloric effect, magnetic ordering temperatures, saturation magnetic moments and anisotropy of sputter-deposited Gd x Cr 1− x alloys with Gd atomic concentrations, x, ranging from 0.13 to 0.52. The complex magnetic nature of the Gd–Cr films was revealed from the M× H isotherms, which do not show saturation even at an applied field of 70 kOe and a temperature of 2 K and do not exhibit a linear behavior at higher temperatures. For some of the samples, the isotherms were used to determine the isothermal entropy variation as a function of temperature, for a change of 50 kOe in the applied magnetic field. The saturation magnetic moment varies with x and follows the dilution law, implying that the Cr atoms do not contribute to the total moment of the Gd–Cr alloys. Both static magnetization and dynamic susceptibility measurements reveal the existence of a magnetic glassy behavior in the alloys, which occurs below a freezing temperature. The existence of anisotropy at low temperatures for all samples was revealed by their M× H hysteresis loops from which the in-plane coercive fields, H c , were determined. A monotonical increase in H c with increasing Gd concentration was observed. ► We studied thin films of Gd x Cr 1− x with x=0.13–0.52. ► Cr atoms do not contribute to the magnetic moment of the alloys. Gd phase is either amorphous or very low crystalline. ► Magnetic and structural properties depend on film deposition parameters and Gd concentration. ► |Δ S M | value observed vary in the range 4.5–8.4 J kg −1 K −1.