Crystallographic, magnetic and calorimetric studies of Ho5Si2Ge2

Abstract Following the discovery of a giant magnetocaloric effect in Gd 5 (Si,Ge) 4 , attention has been extended to R 5 (Si,Ge) 4 with R being other rare-earth elements. In this work, X-ray structural analyses, low- and high-field magnetization measurements and zero-field calorimetric measurements were carried out on Ho 5 Si 2 Ge 2 . Specific heat data were also obtained for nonmagnetic Lu 5 Si 2 Ge 2 as a reference material. In contrast to the general trend of having a ferromagnetic order in the R 5 (Si,Ge) 4 series, Ho 5 Si 2 Ge 2 actually becomes antiferromagnetically ordered with a Neel temperature T N near 25 K. Moreover, an anomalous behavior below T N also prevails in the temperature dependence of both magnetization and specific heat, suggesting further transitions from the antiferromagnetic to other complex magnetic structures.