Crystalline electric-field effects in single-crystal HoNi2B2C

By fitting the temperature-dependent magnetic susceptibility of single-crystal Lu0.976Ho0.024Ni2B2C for applied magnetic fields parallel and perpendicular to the c axis, the crystalline electric-field (CEF) parameters B-n(m), and the CEF energy levels and eigenstates of Ho3+ were determined. Approximate values of the anisotropic exchange constants between the Ho3+ ions in HoNi2B2C were also estimated. Our CEF parameters were checked by calculating magnetization versus held 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 (similar to 90 K) between these levels and the next excited states.