In this study, SrFe_12-xNd_xO₁₉, where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5, was prepared using high-energy ball milling. The prepared samples were characterized by X-ray diffraction (XRD). Using the XRD results, a comparative analysis of crystallite sizes of the prepared powders was carried out by different methods (models) such as the Scherrer, Williamson–Hall (W–H), Halder–Wagner (H–W), and size-strain plot (SSP) method. All the studied methods prove that the average nanocrystallite size of the prepared samples increases by increasing the Nd concentration. The H–W and SSP methods are more accurate than the Scherer or W–H methods, suggesting that these methods are more suitable for analyzing the XRD spectra obtained in this study. The specific saturation magnetization (σ_s), the effective anisotropy constant (K_eff), the field of magnetocrystalline anisotropy (H_a), and the field of shape anisotropy (H_d) for SrFe_12-xNd_xO₁₉ (0 ≤ x ≤ 0.5) powders were calculated. The coercivity (H_c) increases (about 9% at x = 0.4) with an increasing degree of substitution of Fe³⁺ by Nd^3+, which is one of the main parameters for manufacturing permanent magnets.

Combined studies of hard magnetic Nd2Fe14B/α-Fe nanocomposites are performed. They were prepared by mechanical alloying of melt-quenched Nd7.4Pr2.0Fe76.6Co4.2Zr3.4B6.4 and Nd5.8Fe80Co4.9Ti1.5Si2.5B5.3...

The structural transformations and magnetic property changes of the Nd_16.2Fe_balCo_9.9Ga_0.5B_7.5 (SG1, SG2) and Nd_15.0Fe_balGa_2.0B_7.3 (SG3) nanocomposite alloys obtained by melt spinning in the as-quenched state and after annealing at a temperature range of 560–650 °C for 30 min were studied. The methods used were X-ray diffraction analysis, magnetic property measurements, TEM studies, X-ray fluorescence analysis and Mössbauer spectroscopy. Amorphous phase and crystalline phase Nd₂Fe₁₄B (P4₂/mnm) were observed in the alloy after melt spinning. The content of the amorphous phase ranged from 20% to 50% and depended on the cooling rate. Annealing of the alloys resulted in amorphous phase crystallization into Nd₂Fe₁₄B and led to the increased coercivity of the alloys up to 1840 kA/m (23.1 kOe) at 600 °C annealing for 30 min. The alloy with the maximum coercivity had a grain size of the Nd₂Fe₁₄B phase ≈50–70 nm with an Nd-rich phase between grains.

The Ce₂Fe₁₄B intermetallic, like Nd₂Fe₁₄B, has the tetragonal Nd₂Fe₁₄B-type structure (space group P4₂/mnm), in which Ce ions have a mixed-valence state characterized by the coexistence of trivalent 4f¹ and tetravalent 4f⁰ electron states. Despite the fact that the saturation magnetization, magnetic anisotropy field, and Curie temperature of the Ce₂Fe₁₄B intermetallic are substantially lower than those of Nd₂Fe₁₄B and Pr₂Fe₁₄B, Ce₂Fe₁₄B retains the capacity of being able to be used in the manufacturing of rare-earth permanent magnets. Moreover, at low temperatures, the anisotropy field of Се₂Fe₁₄B is higher than that of Nd₂Fe₁₄B, and Се₂Fe₁₄B does not undergo the spin-reorientation transition. In this respect, studies of (Nd, Ce)-Fe-B alloys, which are intended for the improvement of the service characteristics-to-cost ratio, are very relevant. A model and algorithm for calculating the hysteresis loops of uniaxial hard magnetic materials with allowance for the K₁ and K₂ (K₂ > 0 and K₁ > 0 and K₁ < 0) magnetic anisotropy constants were developed and allowed us to obtain data on their effect on the parameters of hysteresis loops for a wide temperature range (0–300 K). The simulation and analysis of hysteresis loops of the quasi-ternary intermetallics (Nd_1−хСе_х)₂Fe₁₄B (х = 0–1) was performed. Results of the simulation indicate that the alloying of the Nd₂Fe₁₄B intermetallic with Ce to x = 0.94 (1) does not completely eliminate the negative effect of spin-reorientation phase transition on the residual magnetization of the (Nd_1−хCe_х)₂Fe₁₄B intermetallic and (2) slightly decreases the slope of magnetization reversal curve.