Low-Temperature Specific Heat and Magnetocaloric Effect in $RCu_2Ge_2$ (R = Dy-Tm) Compounds

The magnetocaloric effect in $RCu_2Ge_2$ (R = Dy-Tm) was investigated by means of specific heat measurements. The compounds order antiferromagnetically at 6.2 K $(DyCu_2Ge_2),$ 5.6 K $(HoCu_2Ge_2),$ 3.0 K $(ErCu_2Ge_2),$ and 3.9 K $(TmCu_2Ge_2),$ and some of them exhibit additional magnetic transitions in the ordered state. In an external magnetic field the low-temperature specific heat changes significantly, which can be attributed to metamagnetic-like transitions. In this temperature region, the investigated samples show distinctly different magnetocaloric effect.