Fe 5 SiB 2 has been synthesized and magnetic measurements have been carried out, revealing that M sat = 0.92 MA/m at T = 300 K. The M vs T curve shows a broad peak around T = 160 K. The anisotropy constant, K 1 , estimated at T = 300 K, is 0.25 MJ/m 3 . Theoretical analysis of Fe 5 SiB 2 system has been carried out and extended to the full range of Fe 5 Si 1−x PxB 2 , Fe 5 P 1−x SxB 2 , and (Fe 1−x Cox) 5 SiB 2 compositions. The electronic band structures have been calculated using the Full-Potential Local-Orbital Minimum-Basis Scheme (FPLO-14). The calculated total magnetic moments are 9.20, 9.15, 9.59 and 2.42µ B per formula units of Fe 5 SiB 2 , Fe 5 PB 2 , Fe 5 SB 2 , and Co 5 SiB 2 , respectively. In agreement with experiment, magnetocrystalline anisotropy energies (MAE's) calculated for T = 0 K changes from a negative (easy-plane) anisotropy −0.28 MJ/m 3 for Fe 5 SiB 2 to the positive (easy-axis) anisotropy 0.35 MJ/m 3 for Fe 5 PB 2 . Further increase of the number of p-electrons in Fe 5 P 1−x SxB 2 leads to an increase of MAE up to 0.77 MJ/m 3 for the hypothetical Fe 5 P 0.4 S 0.6 B 2 composition. Volume variation and fixed spin moment calculations (FSM) performed for Fe 5 SiB 2 show an inverse relation between MAE and magnetic moment in the region down to about 15% reduction of the spin moment. The alloying of Fe 5 SiB 2 with Co is proposed as a practical realization of magnetic moment reduction, which ought to increase MAE. MAE calculated in virtual crystal approximation (VCA) for a full range of (Fe 1−x Cox) 5 SiB 2 compositions reaches the maximum value of 1.16 MJ/m 3 at Co concentration x = 0.3, with the magnetic moment 7.75µ B per formula unit. Thus, (Fe 0.7 Co 0.3 ) 5 SiB 2 is suggested as a candidate for a rare-earth free permanent magnet. For the stoichiometric Co 5 SiB 2 there is an easy-plane magnetization, with the value of MAE = −0.15 MJ/m 3 .

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In this paper, hard magnetic materials for future use in electrical machines are discussed. Commercialized permanent magnets used today are presented and new magnets are reviewed shortly. Specifically, the magnetic MnAl compound is investigated as a potential material for future generator designs. Experimental results of synthesized MnAl, carbon-doped MnAl and calculated values for MnAl are compared regarding their energy products. The results show that the experimental energy products are far from the theoretically calculated values with ideal conditions due to microstructure-related reasons. The performance of MnAl in a future permanent magnet (PM) generator is investigated with COMSOL, assuming ideal conditions. Simplifications, such as using an ideal hysteresis loop based on measured and calculated saturation magnetization values were done for the COMSOL simulation. The results are compared to those for a ferrite magnet and an NdFeB magnet. For an ideal MnAl hysteresis loop, it would be possible to replace ferrite with MnAl, with a reduced weight compared to ferrite. In conclusion, future work for simulations with assumptions and results closer to reality is suggested.

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