Magnetic properties of Fe5SiB2 and its alloys with P, S, and Co
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 17, 174412Article in journal (Refereed) PublishedText
Fe5SiB2 has been synthesized and magnetic measurements have been carried out, revealing that M-sat = 0.92 MA/mat T = 300 K. The M versus 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 Fe5SiB2 system has been carried out and extended to the full range of Fe5Si1-xPxB2, Fe5P1-xSxB2, and (Fe1-xCox)(5)SiB2 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 2.42 mu(B) per formula units of Fe5SiB2, Fe5PB2, Fe5SB2, and Co5SiB2, respectively. In agreement with experiment, magnetocrystalline anisotropy energies (MAE's) calculated for T = 0 K change from a negative (easy-plane) anisotropy -0.28 MJ/m(3) for Fe5SiB2 to the positive (easy-axis) anisotropy 0.35 MJ/m(3) for Fe5PB2. Further increase of the number of p electrons in Fe5P1-xSxB2 leads to an increase of MAE up to 0.77 MJ/m(3) for the hypothetical Fe5P0.4S0.6B2 composition. Volume variation and fixed spin moment calculations (FSM) performed for Fe5SiB2 show an inverse relation between MAE and magnetic moment in the region down to about 15% reduction of the spin moment. The alloying of Fe5SiB2 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 (Fe1-xCox)(5)SiB2 compositions reaches the maximum value of 1.16 MJ/m(3) at Co concentration x = 0.3, with the magnetic moment 7.75 mu(B) per formula unit. Thus, (Fe0.7Co0.3)(5)SiB2 is suggested as a candidate for a rare-earth free permanent magnet. For the stoichiometric Co5SiB2 there is an easy-plane magnetization, with the value of MAE = -0.15 MJ/m(3).
Place, publisher, year, edition, pages
2016. Vol. 93, no 17, 174412
Physical Sciences Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-298092DOI: 10.1103/PhysRevB.93.174412ISI: 000376244900004OAI: oai:DiVA.org:uu-298092DiVA: diva2:944514
FunderGöran Gustafsson Foundation for Research in Natural Sciences and MedicineSwedish Research CouncilEU, FP7, Seventh Framework Programme