TY - JOUR
T1 - Coercivity of titanium-substituted high-temperature permanent magnets
AU - Zhou, J.
AU - Skomski, R.
AU - Sellmyer, D. J.
N1 - Funding Information:
Manuscript received October 13, 2000. This work was supported by the U.S. Air Force Office of Scientific Research and the Defense Advanced Projects Agency through the U.S. Army Research Office. The authors are with Behlen Laboratory of Physics and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588 (e-mail: {jzhou; rskomski}@unlserve.unl.edu; [email protected]). Publisher Item Identifier S 0018-9464(01)06873-X.
PY - 2001/7
Y1 - 2001/7
N2 - 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.
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.
KW - Domain wall pinning
KW - High-temperature permanent magnets
KW - Sm-Co based permanent magnets
KW - Temperature dependence of coercivity
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U2 - 10.1109/20.951221
DO - 10.1109/20.951221
M3 - Conference article
AN - SCOPUS:0035386361
SN - 0018-9464
VL - 37
SP - 2518
EP - 2520
JO - IEEE Transactions on Magnetics
JF - IEEE Transactions on Magnetics
IS - 4 I
T2 - 8th Joint Magnetism and Magnetic Materials -International Magnetic Conference- (MMM-Intermag)
Y2 - 7 January 2001 through 11 January 2001
ER -