Quenching of spin fluctuations in the highly enhanced paramagnetsRCo2(R=Sc,Y,orLu)

Abstract

The low-temperature (1.3-20.0 K) high-magnetic-field (0-10 T) heat capacity and the magnetization and magnetic susceptibility (1.7-300 K) of the strongly Pauli paramagnetic $R{\mathrm{Co}}_2$ ($R=\mathrm{S}\mathrm{c},\mathrm{Y},\mathrm{o}\mathrm{r}\mathrm{L}\mathrm{u}$) compounds with the Mg${\mathrm{Cu}}_2$-type structure were measured. The heat-capacity results for Sc${\mathrm{Co}}_2$, Y${\mathrm{Co}}_2$, and Lu${\mathrm{Co}}_2$ show that the electronic specific-heat constant decreases with increasing magnetic fields (by 7%, 4%, and 10%, respectively, at 10 T). For Y${\mathrm{Co}}_2$ the coefficient of the $T^3$ term ($\beta$) in the heat capacity is found to increase by 18% at 10 T, but for Sc${\mathrm{Co}}_2$ and Lu${\mathrm{Co}}_2$ $\beta$ remains constant within experimental error. Analyses based on several theoretical models of the quenching of spin fluctuations by high magnetic fields suggest that the characteristic spin-fluctuation temperature is ∼20 K for Sc${\mathrm{Co}}_2$, ∼35 K for Y${\mathrm{Co}}_2$, and ∼16 K for Lu${\mathrm{Co}}_2$. The magnetization and the field dependence of the magnetic susceptibility of the same samples as used in the heat-capacity measurements indicate the presence of ferromagnetic impurities in the samples, but the estimated concentrations are sufficiently low that they probably have no effect on the observed heat capacities. Maxwell's thermodynamics relationship between the field dependence of the heat capacity and the temperature dependence of the magnetic susceptibility has been examined.