The Effects of La Doping on the Crystal Structure, Magnetic, and Microwave Absorption Properties of Nd₂Fe₁₄B Compound

The crystal structure, magnetic, and microwave absorption properties of the (Nd_1−xLa_x)₂Fe₁₄B system have been investigated. The La₂Fe₁₄B compound was successfully synthesized and refined, giving a tetragonal structure, space group P4₂/mnm with the Nd₂Fe₁₄B-type structure. The crystal structure parameters of the (Nd_1−xLa_x)₂Fe₁₄B compounds were determined by full-profile Rietveld refinements. The results revealed that all intermediate alloys form a continuous solid solution. The normalized lattice parameters of the (Nd_1−xLa_x)₂Fe₁₄B compounds increase linearly with an increase of La concentration. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Nd₂Fe₁₄B-La₂Fe₁₄B system has been constructed. The remanence (M_r) and coercivity (H_c) of (Nd_1−xLa_x)₂Fe₁₄B (x = 0.00, 0.10, 0.20, 0.30, and 0.40) gradually decrease. The highest reflection loss is − 29.8, − 27.4, − 24.1, − 18.6, and − 14.2 dB at 9.8, 8.9, 7.5, 6.9, and 6.5 GHz, respectively. The absorption peak shifts toward from higher frequency region to lower frequency region and the absorption bandwidth widens with the increase of the La substitution.