Coercivity of titanium-substituted high-temperature permanent magnets

J. Zhou, R. Skomski, David J Sellmyer

Research output: Contribution to journalConference article

16 Citations (Scopus)

Abstract

The temperature dependence of the coercivity of Sm-Co based magnets is investigated by magnetization measurements and model calculations. The Zr-free titanium-substituted Sm-Co material exhibits a positive temperature coefficient dHc/dT of the coercivity (TCC) above room temperature, a reasonable hysteresis-loop shape, and an appreciable coercivity of 12.3 kOe at 500 °C for the nominal composition Sm(Co6.2Cu0.8Ti0.3). The samples were produced by heat-treating the disordered 1:5 alloy commonly referred to as the TbCu7 (or 1: 7) phase. X-ray diffraction analysis shows that, upon annealing at 1165 °C, the starting material segregates into more-or-less stoichiometric 1:5 and 2:17 phases. The TCC is explained by taking into account that two-phase Sm-Co magnets are of the pinning type, that is the coercivity is realized by capturing (or repelling) domain walls at 1:5/2:17 phase boundaries. Starting from a planar-defect approach, the TCC is modeled as a function of the anisotropy constants of the involved phases. The present approach yields a fair agreement between theory and experiment, and explains the existence of a coercivity maximum in terms of the Cu concentration.

Original languageEnglish (US)
Pages (from-to)2518-2520
Number of pages3
JournalIEEE Transactions on Magnetics
Volume37
Issue number4 I
DOIs
StatePublished - Jul 1 2001
Event8th Joint Magnetism and Magnetic Materials -International Magnetic Conference- (MMM-Intermag) - San Antonio, TX, United States
Duration: Jan 7 2001Jan 11 2001

Fingerprint

Coercive force
Titanium
permanent magnets
Permanent magnets
coercivity
titanium
Temperature
Magnets
magnets
Positive temperature coefficient
Domain walls
Phase boundaries
Hysteresis loops
X ray diffraction analysis
domain wall
Magnetization
Anisotropy
hysteresis
Annealing
heat

Keywords

  • Domain wall pinning
  • High-temperature permanent magnets
  • Sm-Co based permanent magnets
  • Temperature dependence of coercivity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

Cite this

Coercivity of titanium-substituted high-temperature permanent magnets. / Zhou, J.; Skomski, R.; Sellmyer, David J.

In: IEEE Transactions on Magnetics, Vol. 37, No. 4 I, 01.07.2001, p. 2518-2520.

Research output: Contribution to journalConference article

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AB - The temperature dependence of the coercivity of Sm-Co based magnets is investigated by magnetization measurements and model calculations. The Zr-free titanium-substituted Sm-Co material exhibits a positive temperature coefficient dHc/dT of the coercivity (TCC) above room temperature, a reasonable hysteresis-loop shape, and an appreciable coercivity of 12.3 kOe at 500 °C for the nominal composition Sm(Co6.2Cu0.8Ti0.3). The samples were produced by heat-treating the disordered 1:5 alloy commonly referred to as the TbCu7 (or 1: 7) phase. X-ray diffraction analysis shows that, upon annealing at 1165 °C, the starting material segregates into more-or-less stoichiometric 1:5 and 2:17 phases. The TCC is explained by taking into account that two-phase Sm-Co magnets are of the pinning type, that is the coercivity is realized by capturing (or repelling) domain walls at 1:5/2:17 phase boundaries. Starting from a planar-defect approach, the TCC is modeled as a function of the anisotropy constants of the involved phases. The present approach yields a fair agreement between theory and experiment, and explains the existence of a coercivity maximum in terms of the Cu concentration.

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