Magnetic properties and specific heat of Tm1−xLuxCu2Si2

The tetragonal TmCu 2 Si 2 compound is the only magnetically ordered material of the RECu 2 Si 2 group for which crystal field parameters were determined. Quadrupole splitting measured by means of Mossbauer spectroscopy showed that two lowest lying states are nonmagnetic singlets. Therefore, this material is likely to have an induced magnetic moment, mainly due to mixing of the two lowest states. We performed specific heat and magnetic susceptibility measurements of Tm 1− x Lu x Cu 2 Si 2 ( x = 0, 0.025, 0.050, 0.10, 0.25, 0.50 and 1) alloys to determine the crystal field level scheme and compare it with the Mossbauer data. The saturation magnetization of the antiferromagnetic phase was calculated to be 3.2 μ B and the moment is directed along the tetragonal c axis. No direct experimental evidence is known to support this prediction.