Specific-heat measurements of ${\mathrm{Ho}}_{\mathrm{x}}$${\mathrm{Y}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Co}}_2$

We report on specific-heat measurements of (${\mathrm{Ho}}_{\mathrm{x}}$ ${\mathrm{Y}}_{1\mathrm{-}\mathrm{x}}$)${\mathrm{Co}}_2$ in the temperature range from 1.5 to 60 K. Sharp peaks at the Curie temperature $T_C$ and the spin-reorientation temperature $T_r$ characterize the temperature dependence for 0.5≤x≤1. For 0.2≤x≤0.4 the magnetic specific heat $C_m$ indicates spin-glass-like behavior, which appears to be in agreement with freezing phenomena observed in magnetic measurements. From the analysis of the magnetic entropy $S_m$, we deduce that the induced Co moment can be referred to as itinerant in the sense of the Stoner theory. In the dilute Ho-concentration range, various anomalies are observed as, e.g., an enhancement of the effective electronic specific heat γ and the effective Debye temperature ${\mathrm{FTHETA}}_D$ (of about 400% and 100%, respectively) and significant upturns of the $C_p$/T versus $T^2$ graphs together with a pronounced reduction of the magnetic entropy. These anomalies are discussed in terms of spin fluctuations; the loss of the magnetic entropy for x<0.2 may point to an instability of the Ho moment.