Abstract
The effects of substitutional and interstitial atoms on the magnetic and magnetocaloric properties are investigated for RNi (R is rare earth) compounds attractive for magnetic solid-state cooling at cryogenic temperatures. We focused on combining weakly and highly anisotropic rare earth compounds and obtained GdxDy1-xNi (x = 0.1 and 0.9) compounds and their GdxDy1-xNiH3 hydrides.
We observed a considerable decrease in Curie temperatures (T-C) in the hydrides GdxDy1-xNiH3 compared to their parent alloys. The magnetocaloric effect (MCE) values of GdxDy1-xNiHy (y = 0 and 3) in the vicinity of T-C were obtained and compared with literature data for the final GdNi and DyNi compounds.
The maximum specific isothermal entropy changes -Delta s(T) at mu(0)Delta H = 5 T were 14.5, 17, and 17.5 J kg(-1)K(-1) for GdNi, Gd0.9Dy0.1Ni, and Gd0.9Dy0.1NiH3, respectively. For DyNi, Gd0.1Dy0.9Ni, and Gd0.1Dy0.9NiH3, they were -Delta s(T) = 18, 15.5, and 12.5 J kg(-1)K(-1) at mu(0)Delta H = 5 T, respectively. -Delta s(T)(H) in Gd0.9Dy0.1NiH3 at T >= TC linearly increased in fields up to 7 T, while Gd0.1Dy0.9NiH3 at T >= T-C showed a plateau-like magnetocaloric effect at mu(0)Delta H = 5 and 7 T.
The observed effects were explained based on altered exchange and magnetocrystalline interactions in the modified compounds.