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Title: Superferrimagnetism in hard Nd-Fe-B thick films, an original concept for coercivity enhancement

In a number of applications (automotive, wind generators), RFeB magnets are parts of systems which operate at temperatures in the range of 160 °C–180 °C. At these high temperatures, coercivity is preserved by substituting Dy atoms for a part of the Nd ones. The enhanced coercivity obtained may be associated to the high magnetocrystalline anisotropy of Dy atoms, which diffuse into the R{sub 2}Fe{sub 14}B phase. The introduction of Dy, however, induces a reduction in the remanent magnetization. Furthermore, Dy is an expensive and strategic material. In this study, we explore a radically different approach to coercivity. A magnetic layer is deposited at the surface of the hard grains, this layer being exchange coupled to the main hard phase in a way that its magnetization is antiparallel to it. Under an applied field that tends to reverse the main phase magnetization, the surface layer, the magnetization of which is along the field, works against reversal. This is the concept of superferrimagnetism. In order to test its impact on the coercivity of real systems, magnetically hard thick films of NdFeB have been sandwiched between thin layers of Gd/Fe, which were transformed to GdFe{sub 2} upon annealing. Coercivity enhancement was achieved compared to amore » reference NdFeB single layer.« less
Authors:
; ; ;  [1] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Univ. Grenoble Alpes, Institut NEEL, F-38042 Grenoble (France)
  2. (France)
  3. (Brazil)
Publication Date:
OSTI Identifier:
22273725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 17; Conference: 55. annual conference on magnetism and magnetic materials, Atlanta, GA (United States), 14-18 Nov 2010; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; ANISOTROPY; ANNEALING; COERCIVE FORCE; COMPARATIVE EVALUATIONS; IRON BORIDES; LAYERS; MAGNETIC MATERIALS; MAGNETIZATION; NEODYMIUM COMPOUNDS; SURFACES; TEMPERATURE RANGE 0400-1000 K; THIN FILMS