Magnetic properties of Fe${}_5$SiB${}_2$ and its alloys with P, S, and Co

Abstract

Fe${}_5$SiB${}_2$ has been synthesized and magnetic measurements have been carried out, revealing that M${}_{\text{sat}}$ = 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${}_{1-x}$P${}_x$B${}_2$, Fe${}_5$P${}_{1-x}$S${}_x$B${}_2$, and (Fe${}_{1-x}$Co${}_x$)${}_5$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 2.42${\mu }_B$ 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${}_{1-x}$S${}_x$B${}_2$ 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${}_{1-x}$Co${}_x$)${}_5$SiB${}_2$ compositions reaches the maximum value of 1.16 MJ/m${}^3$ at Co concentration x = 0.3, with the magnetic moment 7.75${\mu }_B$ 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.

11 pages, 14 figures

References in corpus (9)

• Electronic structure and magnetic properties of L1_0 binary alloys
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• A study of the physical properties of single crystalline Fe5B2P
• Origin of the spin reorientation transitions in (Fe${}_{1-x}$Co${}_x$)${}_2$B alloys
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• Ab initio study of pressure-induced phase transition, band gaps and X-ray photoemission valence band spectra of YVO${}_4$

Cited by in corpus (4)

• Ab initio study of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10 FeNi (tetrataenite)
• Magnetocrystalline anisotropy of Fe5PB2 and its alloys with Co and 5d elements: a combined first-principles and experimental study
• Magnetic properties of the Fe${}_5$SiB${}_2$-Fe${}_5$PB${}_2$ system
• Structural transformation and magnetic properties of (Fe${}_{0.7}$Co${}_{0.3}$)${}_2$B alloys doped with 5$d$ elements: A combined first-principles and experimental study