TY - JOUR
T1 - Anisotropy and orbital moment in Sm-Co permanent magnets
AU - Das, Bhaskar
AU - Choudhary, Renu
AU - Skomski, Ralph
AU - Balasubramanian, Balamurugan
AU - Pathak, Arjun K.
AU - Paudyal, Durga
AU - Sellmyer, David J.
N1 - Funding Information:
This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. The Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University of Science and Technology under Contract No. DE-AC02-07CH11358. R.C. and D.P. would like to acknowledge Ed Moxley for maintaining and updating computational facilities and software packages including the Raman cluster and the wien2k program. The work in Nebraska was supported by the U.S. Department of Energy (Grant No. DE-FG02-04ER46152) and performed in part in the Nebraska Nanoscale Facility and the Nebraska Center for Materials and Nanoscience which are supported by NSF NNCI No. 1542182, and the Nebraska Research Initiative. Thanks are due to J. E. Shield and S. R. Valloppilly for assistance and helpful discussions.
Publisher Copyright:
© 2019 American Physical Society.
PY - 2019/7/18
Y1 - 2019/7/18
N2 - Structural and magnetic properties of iron-free and iron-substituted SmCo5 have been investigated theoretically and experimentally. The nanocrystalline ribbons of SmCo5-xFex(0≤x≤2), which were produced by rapid solidification, crystallize in the hexagonal CaCu5 structure for x≤0.75. Small Fe additions (x=0.25) substantially improve the coercivity, from 0.45 to 2.70 T, which we interpret as combined intrinsic and extrinsic effect. Most of our findings are consistent with past samarium-cobalt research, but some are at odds with findings that have seemingly been well established through decades of rare-earth transition-metal research. In particular, our local spin-density approximation with Hubbard parameter calculations indicate that the electronic structure of the Sm atoms violates Hund's rules and that the orbital moment is strongly quenched. Possible reasons for the apparent disagreement between theory and experiment are discussed. We explicitly determine the dependence of the Sm 4f charge distribution, arguing that an accurate density-functional description of SmCo5 is a challenge to future research.
AB - Structural and magnetic properties of iron-free and iron-substituted SmCo5 have been investigated theoretically and experimentally. The nanocrystalline ribbons of SmCo5-xFex(0≤x≤2), which were produced by rapid solidification, crystallize in the hexagonal CaCu5 structure for x≤0.75. Small Fe additions (x=0.25) substantially improve the coercivity, from 0.45 to 2.70 T, which we interpret as combined intrinsic and extrinsic effect. Most of our findings are consistent with past samarium-cobalt research, but some are at odds with findings that have seemingly been well established through decades of rare-earth transition-metal research. In particular, our local spin-density approximation with Hubbard parameter calculations indicate that the electronic structure of the Sm atoms violates Hund's rules and that the orbital moment is strongly quenched. Possible reasons for the apparent disagreement between theory and experiment are discussed. We explicitly determine the dependence of the Sm 4f charge distribution, arguing that an accurate density-functional description of SmCo5 is a challenge to future research.
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U2 - 10.1103/PhysRevB.100.024419
DO - 10.1103/PhysRevB.100.024419
M3 - Article
AN - SCOPUS:85072853860
VL - 100
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 2469-9950
IS - 2
M1 - 024419
ER -