Spin reorientation and crystal-field interaction inTbFe12−xTixsingle crystals

The magnetic properties of ${\mathrm{TbFe}}_{12\ensuremath{-}x}{\mathrm{Ti}}_{x}$ single crystals with $x=0.8--1.4$ have been investigated in detail using ac and dc susceptibility and high-field magnetization measurements. A first-order spin reorientation transition from a basal plane easy magnetization direction at low temperatures to an axial easy magnetization direction at high temperatures occurs for all the investigated compounds. The spin reorientation temperatures have been determined by combining ac and dc susceptibility measurements and its dependence on both the Ti content and the applied magnetic field has been studied. A first-order magnetization process is observed below a certain temperature when the magnetic field is applied along the [001] crystallographic direction. The dependence of the transition critical field on the Ti content has been analyzed. The magnetic behavior has been interpreted using a two-sublattices model for the magnetic structure, in the frame of a crystal-electric-field--mean-field model. The parameters describing the crystal-field interaction in ${\mathrm{TbFe}}_{12\ensuremath{-}x}{\mathrm{Ti}}_{x}$ compounds have been determined. The calculated magnetic behavior shows a good agreement with experimental results in a wide temperature range.