Phase analysis and magnetic properties of RTiFe11−xCox (R=Y,Gd) (x=0–11)

Abstract

Both as-cast and 1000 °C annealed RTiFe11 samples are nearly single phase with a small amount of Fe2Ti. Small amounts of Co additions do not change the microstructure, but the minor phase changed to a Fe,Co,Ti solid solution. At high Co concentration, as-cast samples are multiphase [1-12, 2-17, (Fe,Co,Ti)] and high-temperature (∼1200 °C) annealing is needed in order to produce a single-phase microstructure. Results of x-ray analysis and magnetic measurements show that YTiFe11, YTiCo11, GdTiFe11, and GdTiCo11 are uniaxial and their anisotropy fields at room temperature are 22, 18, 33, and 25 kOe, respectively. Therefore, Fe and Co sublattices are uniaxial with Fe sublattice anisotropy stronger than that of Co. In the intermediate range of composition, there is a conical-planar region for both Y and Gd systems and spin reorientations with temperature were observed. In general, the anisotropy behavior of the RTiFe11−xCox systems (R=Y,Gd) is similar but opposite to their counterpart of R2Fe17−xCox. This is due to the similarity of their crystal structure, as both are derivatives of 1-5. However, the strong contribution from the K2 anisotropy constant makes the anisotropy phase diagrams of 1-12 more complicated than those of 2-17.