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Title: Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets

Abstract

Rare-earth (R) permanent magnets of R2Fe14B have technological importance due to their high energy products, and they have two R-sites (Wyckoff 4f and 4g, with four-fold multiplicity) that affect chemistry and valence. Designing magnetic behavior and stability via alloying is technologically relevant to reduce critical (expensive) R-content while retaining key properties; cerium, an abundant (cheap) R-element, offers this potential. We calculate magnetic properties and Ce site preference in (R1-xCex)2Fe14B [R=La,Nd] using density functional theory (DFT) methods—including a DFT+U scheme to treat localized 4f-electrons. Fe moments compare well with neutron data—almost unaffected by Hubbard U, and weakly affected by spin-orbit coupling. In La2Fe14B, Ce alloys for 0 ≤ x ≤ 1 and prefers smaller R(4f) sites, as observed, a trend we find unaffected by valence. Whereas, in Nd2Fe14B, Ce is predicted to have limited alloying (x ≤ 0.3) with a preference for larger R(4g) sites, resulting in weak partial ordering and segregation. The Curie temperatures versus x for (Nd,Ce) were predicted for a typical sample processing and verified experimentally.

Authors:
 [1];  [1];  [1];  [1]
  1. Ames Laboratory
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
OSTI Identifier:
1080070
Report Number(s):
IS-J 7933
Journal ID: ISSN 0003-6951
DOE Contract Number:  
DE-AC02-07CH11358
Resource Type:
Journal Article
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 102; Journal Issue: 4; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; boron alloys, cerium alloys, Curie temperature, density functional theory, ferromagnetic materials, Hubbard model, iron alloys, neodymium alloys, permanent magnets, segregation, spin-orbit interactions

Citation Formats

Alam, Aftab, Khan, Mahmud, McCallum, R. W., and Johnson, Duane D. Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets. United States: N. p., 2013. Web. doi:10.1063/1.4789527.
Alam, Aftab, Khan, Mahmud, McCallum, R. W., & Johnson, Duane D. Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets. United States. doi:10.1063/1.4789527.
Alam, Aftab, Khan, Mahmud, McCallum, R. W., and Johnson, Duane D. Mon . "Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets". United States. doi:10.1063/1.4789527.
@article{osti_1080070,
title = {Site-preference and valency for rare-earth sites in (R-Ce)2Fe14B magnets},
author = {Alam, Aftab and Khan, Mahmud and McCallum, R. W. and Johnson, Duane D},
abstractNote = {Rare-earth (R) permanent magnets of R2Fe14B have technological importance due to their high energy products, and they have two R-sites (Wyckoff 4f and 4g, with four-fold multiplicity) that affect chemistry and valence. Designing magnetic behavior and stability via alloying is technologically relevant to reduce critical (expensive) R-content while retaining key properties; cerium, an abundant (cheap) R-element, offers this potential. We calculate magnetic properties and Ce site preference in (R1-xCex)2Fe14B [R=La,Nd] using density functional theory (DFT) methods—including a DFT+U scheme to treat localized 4f-electrons. Fe moments compare well with neutron data—almost unaffected by Hubbard U, and weakly affected by spin-orbit coupling. In La2Fe14B, Ce alloys for 0 ≤ x ≤ 1 and prefers smaller R(4f) sites, as observed, a trend we find unaffected by valence. Whereas, in Nd2Fe14B, Ce is predicted to have limited alloying (x ≤ 0.3) with a preference for larger R(4g) sites, resulting in weak partial ordering and segregation. The Curie temperatures versus x for (Nd,Ce) were predicted for a typical sample processing and verified experimentally.},
doi = {10.1063/1.4789527},
journal = {Applied Physics Letters},
issn = {0003-6951},
number = 4,
volume = 102,
place = {United States},
year = {2013},
month = {1}
}