Crystal Field of Some Monoclinic Rare-Earth Chlorides

The 15 crystal-field parameters Bkq=〈rk〉Akq for monoclinic ErCl3·6H2O were found to be B20=116,B22=158,B̄22=−262,B40=−88,B42=−193,B̄42=346,B44=332,B̄44=158,B60=−9.8,B62=−70,B̄62=141,B64=238,B64=−119,B66=238,B̄66=−11.When used together with Wybourne's free-ion wavefunctions, the field adequately explains most of the observed Stark and Zeeman splittings. The Bkq, modified by the calculated 〈rk〉 of Freeman and Watson, are appropriate for several ions and, in all, account for about 200 independent data. A possible systematic variation of the Akq for odd and even electron ions is pointed out. The Zeeman splittings of the 6P7/2 and 6P5/2 states of GdCl3·6H2O are explained, and the use of the Gd3+ ion as a crystal-field probe is discussed.