Rapid solidification of Nd1+XFe11Ti compounds: Phase formation and magnetic properties

The effects of compositional variations and different annealing regimes in Nd(Fe,Ti)₁₂ alloys were studied in terms of phase formation and magnetic properties analysis. Nd_xFe₁₁Ti (x = 1.05, 1.10, 1.15, 1.20) alloys were produced by rapid solidification through suction casting technique. The effect of Nd content and post annealing were investigated in the temperature range of 700–1200 °C. Single 1:12 phase samples were obtained at temperatures between 1150 and 1200 °C for compositions with Nd concentration of 1.15 and 1.20. Intrinsic magnetic properties and magnetization reversal were studied for 1:12 single phase samples, revealing uniaxial anisotropy with anisotropy field (H_A) of 1.08T and saturation magnetization of 137 Am²kg⁻¹ at room temperature. In addition, the demagnetization mechanism in bulk polycrystalline samples was analyzed by means of Kerr microscopy under applied magnetic fields. Magnetization reversal process starts at the twin boundary, which acts as a nucleation center for the reversal domain, and coupling between adjacent grains is also observed. These may be part of the reasons for the observed low coercivity in the NdFe₁₁Ti systems. The findings of the present study leads to a better understanding of the relation between magnetic properties and microstructure, and can open new strategies to obtain coercivity in this 1:12 phase system and, possibly, in the corresponding nitride.