155Gd Mössbauer effect and magnetic properties of novel RT2B2C compounds with TNi, Co

Abstract We have prepared the compounds GdNi 2 B 2 C and GdCo 2 B 2 C and investigated their magnetic properties by means of 155 Gd Mossbauer spectroscopy. From the temperature dependence of the hyperfine field, we derived that these two compounds give rise to magnetic ordering at 5.5±0.5 K and 21±1 K respectively. Large values of the electric field gradient V zz were found, reminiscent of compounds of the related ThCr 2 Si 2 type. A quantitative explanation of the origin of these field gradients is presented by ab initio band structure calculations. The experimental values of V zz have been used to estimate values for the second-order crystal field parameter in GdNi 2 B 2 C ( A 2 0 =−428 Ka 0 −2 ) and GdCo 2 B 2 C ( A 2 0 =−346 Ka 0 −2 ).