Crystalline electric-field effects in single-crystalHoNi2B2C

By fitting the temperature-dependent magnetic susceptibility of single-crystal ${\mathrm{Lu}}_{0.976}$ ${\mathrm{Ho}}_{0.024}$ ${\mathrm{Ni}}_2$ ${\mathrm{B}}_2$C for applied magnetic fields parallel and perpendicular to the c axis, the crystalline electric-field (CEF) parameters ${\mathit{B}}_{\mathit{n}}^{\mathit{m}}$, and the CEF energy levels and eigenstates of ${\mathrm{Ho}}^{3+}$ were determined. Approximate values of the anisotropic exchange constants between the ${\mathrm{Ho}}^{3+}$ ions in ${\mathrm{HoNi}}_2$ ${\mathrm{B}}_2$C were also estimated. Our CEF parameters were checked by calculating magnetization versus field isotherms and good agreement with experiment was found. The energy-level scheme shows two singlets and a doublet below 10 K and a large energy gap (∼90 K) between these levels and the next excited states. © 1996 The American Physical Society.