Magnetic entropy change and magnetocaloric effect of DyNiSi3, Dy2Ni3Si5, DyNiSi2 and HoNiSi0.33Ga67 antiferromagnets

Magnetic properties, magnetic entropy change and magnetocaloric effect of the polycrystalline SmNiGe3-type DyNiSi3, U2Co3Si5-type Dy2Ni3Si5, CeNiSi2-type DyNiSi2 and CeCu2-type HoNiSi0.33Ga0.67 antiferromagnets have been studied by bulk magnetization measurements. In field of 100 Oe DyNiSi3, Dy2Ni3Si5, DyNiSi2 and HoNiSi0.33Ga0.67 show Neel temperature (T-N) of 21 K, 19 K, 9 K and 4 K, respectively. At 2 K, above critical field (H-crit) of 28 kOe for DyNiSi3, 10 kOe for Dy2Ni3Si5, 25 kOe for DyNiSi2 and similar to 1 kOe for HoNiSi0.33Ga0.67 they are soft ferromagnets and HoNiSi0.33Ga0.67 shows ferromagnetic ordering below T-C = 5 K in a field of 5 kOe. Magnetic entropy changes (Delta S-m) of DyNiSi3, Dy2Ni3Si5, DyNiSi2 and HoNiSi0.33Ga0.67 exhibit high-temperature negative and low temperature positive components around Neel temperature up to critical field with decreasing and disappearance of positive component of Delta S-m above critical field, which indicates the transformation from antiferromagnetic to ferromagnetic states. From these compounds, HoNiSi0.33Ga0.67 shows largest magnetic entropy change of -15.4 J/kg.K at 8 K for a field change of 050 kOe.