Specific heat of Cu substituted GdNiSi

Abstract

Abstract The specific heat of magnetic regenerator materials affects the efficiency of cryocoolers below 10 K. GdNiSi with the orthorhombic TiNiSi-type structure shows antiferromagnetic order at 11 K. To tune the magnetic transition temperature below 10 K, Cu substituted GdNiSi alloys were prepared. Powder X-ray diffraction and specific heat measurements were performed to study the effect of Cu substitution on the crystal structure and magnetic transition temperature. Increasing Cu content, the secondary phase which may be the hexagonal BeZrSi-type GdNi1−x Cu x Si is observed. The peak of the specific heat for x ≤ 0.2 was shifted higher temperature (13 K) due to the magnetic transition, though the unit cell volume of the TiNiSi-type structure slightly increased with increasing x. This result possibly originates from the increase of the RKKY interaction for the sinusoidal curve due to an increase of the intersite distance of Gd-ions.