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

Abstract

\u3cp\u3eWe have prepared the compounds GdNi\u3csub\u3e2\u3c/sub\u3eB\u3csub\u3e2\u3c/sub\u3eC and GdCo\u3csub\u3e2\u3c/sub\u3eB\u3csub\u3e2\u3c/sub\u3eC and investigated their magnetic properties by means of \u3csup\u3e155\u3c/sup\u3eGd Mössbauer 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\u3csub\u3ezz\u3c/sub\u3e were found, reminiscent of compounds of the related ThCr\u3csub\u3e2\u3c/sub\u3eSi\u3csub\u3e2\u3c/sub\u3e type. A quantitative explanation of the origin of these field gradients is presented by ab initio band structure calculations. The experimental values of V\u3csub\u3ezz\u3c/sub\u3e have been used to estimate values for the second-order crystal field parameter in GdNi\u3csub\u3e2\u3c/sub\u3eB\u3csub\u3e2\u3c/sub\u3eC (A\u3csub\u3e2\u3c/sub\u3e \u3csup\u3e0\u3c/sup\u3e=-428Ka\u3csub\u3e0\u3c/sub\u3e \u3csup\u3e-2\u3c/sup\u3e) and GdCo\u3csub\u3e2\u3c/sub\u3eB\u3csub\u3e2\u3c/sub\u3eC (A\u3csub\u3e2\u3c/sub\u3e \u3csup\u3e0\u3c/sup\u3e=-346Ka\u3csub\u3e0\u3c/sub\u3e \u3csup\u3e-2\u3c/sup\u3e).\u3c/p\u3