The anion and cation effects in the magnetic anisotropy of rare-earth compounds: Charge screening by conduction electrons

The formation of magnetic anisotropy (MA) in rare-earth compounds with tran sition metals has been analyzed. The screening of the charges creating the crystal field by conduction electrons has been shown to play an important r ole. The calculations took into account the Friedel charge-density oscillat ions. The model used for RCo5 is the point-charge crystal field including n onuniform screening by conduction electrons with an anisotropic Fermi surfa ce. The mechanisms of strong MA due to light-element impurities (hydrogen a nd nitrogen) are considered. The effective charge of an impurity can heavil y depend on its ionic radius and the characteristics of the Fermi surface ( in particular, on the Fermi momentum k(F)) of the screening electrons. The screening of the cation and anion charge in hydrides and nitrides based on the R2Fe17 and RFe11Ti intermetallic compounds is discussed. (C) 2000 MAIK "Nauka/ Interperiodica".