MAGNETIC-ANISOTROPY AND SPIN-REORIENTATION TRANSITIONS IN RFE(11)TI (R=ND, TB, DY, ER) RARE-EARTH INTERMETALLICS

RFe(11)Ti rare-earth intermetallics (R = Nd, Tb, Dy, Er) which show te mperature-induced spin-reorientation transitions (SRT) were investigat ed. The temperature dependences of the rare-earth anisotropy constants were calculated using the single-ion model. By fitting the experiment al data a set of crystal-field and exchange-field parameters for R(3+) ions was deduced. The temperature dependence of the first-order magne tization process fields was calculated for NdFe11Ti and ErFe11Ti withi n the model. The calculated spin-reorientation transition in NdFe11Ti observed at T-s = 189 K is of first order with a discontinuous jump of the magnetization angle. Present calculations show that a first-order transition occurs in DyFe11Ti at low temperatures. A second-order SRT from 'easy axis' to 'easy cone' exists in ErFe11Ti. A first-order SRT 'easy axis'-'easy plane' is predicted theoretically in TbFe11Ti. The calculated curves of the temperature dependence of the anisotropy fiel ds and the critical fields of the first-order magnetization processes for RFe(11)Ti using the fitted crystal- and exchange-field parameters are in good agreement with the experimental data over a wide temperatu re range.