Specific heat and magnetic ordering of NdNi2B2C

In this work, the specific heat of NdNi2B2C was computed with the three sets of crystal-field parameters proposed by previous authors. All curves of the heat capacity plotted with the calculated results exhibit sharp peaks around the magnetic transition temperature T-N as experimentally observed. To understand the mechanism of its magnetic ordering, we also calculated the magnetization of the material in low temperature region with the ground crystal-field (CF) level, the two lowest CF levels. and the full CF levels of J = 9/2 multiplet respectively for comparison. Using the two eiqenstates of the ground CF level, we derived a formula for J(x) with mean-field approach for theoretical analysis. Both our numeric and theoretical results suggest that the two lowest CF levels play dominant roles in the magnetic process of the material below T-N. It is also very interesting to notice that the ground CF level itself results in a largerT(N), but the inclusion of the first excited CF doublet in calculations instead hinders the magnetic ordering. leading to a weakly reduced transition temperature. (c) 2007 Elsevier B.V. All rights reserved.