Magnetic anisotropy and spin-reorientation transitions in RFe 11Ti (R = Nd, Tb, Dy, Er) rare-earth intermetallics

Abstract

RFe 11Ti rare-earth intermetallics (R = Nd, Tb, Dy, Er) which show temperature-induced spin-reorientation transitions (SRT) were investigated. The temperature dependences of the rare-earth anisotropy constants were calculated using the single-ion model. By fitting the experimental data a set of crystal-field and exchange-field parameters for R 3+ ions wassb deduced. The temperature dependence of the first-order magnetization process fields was calculated for NdFe 11Ti and ErFe 11Ti within the model. The calculated spin-reorientation transition in NdFe 11Ti 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 DyFe 11Ti at low temperatures. A second-order SRT from ‘easy axis’ to ‘easy cone’ exists in ErFe 11Ti. A first-order SRT ‘easy axis’-‘easy plane’ is predicted theoretically in TbFe 11Ti. The calculated curves of the temperature dependence of the anisotropy fields and the critical fields of the first-order magnetization processes for RFe 11Ti using the fitted crystal- and exchange-field parameters are in good agreement with the experimental data over a wide temperature range.