Crystal field and magnetic properties in some cubic holmium compounds

Crystal-field parameters have been determined by neutron spectroscopy on some holmium intermetallic compounds of CsCl structure (HoCu, HoAg, HoZn, HoMg). The variation of parameters with the alloyed metal is very similar to the results previously observed on isomorphous erbium compounds. The behavior of $A_4 〈r^4〉$ seems to reflect the influence of $d$ electrons of the alloyed metal. The fourth-order terms present a significant shift between Ho and Er series, whereas the sixth-order ones always remain of the same order of magnitude. We discuss the influence of these parameters on the magnetic properties in the ordered state.