Susceptibility of spin-fluctuation compounds in high magnetic fields

The differential susceptibilities of the spin-fluctuation compounds ${\mathrm{TiBe}}_2$, ${\mathrm{UAl}}_2$, ${\mathrm{UCo}}_2$, and ${\mathrm{UPt}}_3$ have been measured at low temperatures as a function of magnetic field up to 40 T. A systematic relation is observed between the signs of the second derivatives of the susceptibility with respect to field and temperature. A characteristic field $H_{\mathrm{sf}}$ and a characteristic temperature $T_{\mathrm{sf}}$ are defined by the inflection points in the χ(H) and χ(T) curves, respectively. It turns out that ${\mu }_B$ $H_{\mathrm{sf}}$ is of the order of ${\mathrm{kT}}_{\mathrm{sf}}$.