Physical properties of nitrogenated RFe11Ti intermetallic compounds (R=Ce, Pr and Nd) with ThMn12-type structure

Iron-rich ternary intermetallics RFe₁₁Ti (R=Ce, Pr and Nd) with a ThMn₁₂-type structure and their nitrides RFe₁₁TiN_x (x≈1.5) were carefully prepared. After characterizing them by metallographic and microscopic analyses, we studied structural and magnetic properties of the mother compounds and their nitrides. The lattice expansion due to nitrogenation is mainly along the c-axis for the Pr and Nd systems, while that is mainly along the a-axis for the Y system. The lattice expansion of the Ce system is isotropic but the volume expansion is the largest, indicating that the Ce-4f electron state dramatically changes upon nitrogen uptake. The Curie temperature, T_C, increases by 200 K reaching T_C≈720 K for the Pr and Nd system. The saturation magnetization, M_S, increases ≈ 10% by nitrogenation and reaches 1.8–1.9 T at 4.2 K and 1.5 T at 300 K for Pr and Nd systems. The anisotropy field, υ₀H_A is estimated to be more than 20 T at 4.2 K and 7 T at 300 K. The improvement of magnetic properties upon nitrogenation is briefly discussed in terms of the calculated band structure. The results obtained at 300 K indicate that the Pr and Nd nitrides are promising as permanent magnetic application.