Effect of Ni substitution on the magnetic and magnetocaloric properties of the Dy(Co1−xNix)2 Laves phase

Abstract

Structural, magnetic and magnetocaloric properties of Dy(Co1−xNix)2 (x = 0, 0.02, 0.04, 0.06 and 0.1) alloys were studied by x-ray diffraction (XRD) and magnetic measurements. The XRD analysis shows that all samples crystallize in the cubic MgCu2-type structure. The ordering temperature TC decreases from 143 to 92 K with increasing Ni content up to 0.1, which is attributed to the decrease in the exchange interactions. The isothermal entropy changes ΔS as a function of temperature in different magnetic fields were determined. All samples show a large isothermal entropy change and ΔSmax remains approximately constant over the temperature range limited by the Curie temperatures of the Dy(Co1−xNix)2 series (92–143 K). The relative cooling power increases with the Ni content; it passes from 287 to 344 J kg−1 for x varying from 0 to 0.1 under 5 T. The origin of the magnetocaloric effect in Dy(Co1−xNix)2 alloys is discussed.