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Title: Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets

Abstract

The relation between the macroscopic spontaneous magnetization reversal (magnetic viscosity) of (NdDySm)(FeCo)B alloys and the spectral characteristics of magnetic noise, which is caused by the random microscopic processes of thermally activated domain wall motion in a potential landscape with uniformly distributed potential barrier heights, is found.

Authors:
; ; ;  [1]; ; ;  [2]
  1. Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)
  2. All-Russia Institute of Aviation Materials (Russian Federation)
Publication Date:
OSTI Identifier:
22617206
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 123; Journal Issue: 2; Other Information: Copyright (c) 2016 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALLOYS; BORON COMPOUNDS; COBALT COMPOUNDS; DYSPROSIUM COMPOUNDS; IRON COMPOUNDS; MAGNETIZATION; NEODYMIUM COMPOUNDS; NOISE; PERMANENT MAGNETS; RARE EARTH COMPOUNDS; SAMARIUM COMPOUNDS; TERNARY ALLOY SYSTEMS; TRANSITION ELEMENT COMPOUNDS; VISCOSITY

Citation Formats

Dmitriev, A. I., E-mail: aid@icp.ac.ru, Talantsev, A. D., E-mail: artgtx32@mail.ru, Kunitsyna, E. I., Morgunov, R. B., Piskorskii, V. P., Ospennikova, O. G., and Kablov, E. N.. Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets. United States: N. p., 2016. Web. doi:10.1134/S106377611606011X.
Dmitriev, A. I., E-mail: aid@icp.ac.ru, Talantsev, A. D., E-mail: artgtx32@mail.ru, Kunitsyna, E. I., Morgunov, R. B., Piskorskii, V. P., Ospennikova, O. G., & Kablov, E. N.. Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets. United States. doi:10.1134/S106377611606011X.
Dmitriev, A. I., E-mail: aid@icp.ac.ru, Talantsev, A. D., E-mail: artgtx32@mail.ru, Kunitsyna, E. I., Morgunov, R. B., Piskorskii, V. P., Ospennikova, O. G., and Kablov, E. N.. Mon . "Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets". United States. doi:10.1134/S106377611606011X.
@article{osti_22617206,
title = {Magnetic noise as the cause of the spontaneous magnetization reversal of RE–TM–B permanent magnets},
author = {Dmitriev, A. I., E-mail: aid@icp.ac.ru and Talantsev, A. D., E-mail: artgtx32@mail.ru and Kunitsyna, E. I. and Morgunov, R. B. and Piskorskii, V. P. and Ospennikova, O. G. and Kablov, E. N.},
abstractNote = {The relation between the macroscopic spontaneous magnetization reversal (magnetic viscosity) of (NdDySm)(FeCo)B alloys and the spectral characteristics of magnetic noise, which is caused by the random microscopic processes of thermally activated domain wall motion in a potential landscape with uniformly distributed potential barrier heights, is found.},
doi = {10.1134/S106377611606011X},
journal = {Journal of Experimental and Theoretical Physics},
number = 2,
volume = 123,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}
  • Major and minor hysteresis loop measurements have been performed on Nd{sub 15.1}Fe{sub 76.9}B{sub 8} sintered magnet. The coercivity as a function of the maximum magnetizing field has been determined. This dependence appeared to be typical of nucleation hardened materials. The domain structure behavior during the magnetization reversal has been observed on the surface parallel to the alignment direction of the sample. Domain structure photographs have been correlated with suitable points on both virgin and demagnetization curves, respectively. It was stated from this observation that the demagnetization process occurs by the nucleation of reversed domains at the grain boundaries.
  • High coercive force Sm/sub 2/(Co,Fe,Cu,Zr)/sub 17/ type magnets with Sm partly replaced by neodymium, praseodymium and mischmetal were investigated. Magnetic properties including open circuit temperature effects on remanence were measured for these magnets. The results show that coercive force began to decrease when Sm was substituted with any of the rare earths investigated. Usable coercive force can still be maintained at more than 50% substitution of Sm by mischmetal and up to 20% substitution by neodymium. With neodymium and praseodymium substitutions, the expected increase of residual induction B /sub r/ did not occur, presumably due to lessened orientation. Open circuitmore » remanence measurements show that these magnets have temperature effects only slightly higher than the Sm only magnet and are better than the new neodymiumiron-boron magnet.« less
  • Results of experiments to study the effect of grain size and grain-size distribution on the intrinsic coercivity and the hysteresis loop of sintered Fe-Nd-B magnets are presented. It is shown that the intrinsic coercivity decreases as the average grain size of the magnet is increased. It is also shown that the intrinsic coercivity decreases linearly with the logarithm of the square of the grain size. This is consistent with the predictions made based upon the statistical model developed in Part I. An increase in the sintering temperature leads to an increase in the average grain size, which consequently leads tomore » a narrower hysteresis loop and lower intrinsic coercivity compared to magnets sintered at a lower temperature. It is also shown that a heterogeneous grain-size distribution, such as a bimodal distribution, causes kinks to appear in the second quadrant of the hysteresis loop. By examining magnets with different fractions of large grains, the prediction that the magnitude of the kinks increases with the volume fraction of the large grains, has been verified experimentally.« less
  • In discussing a previous statistical model for the problem of coercivity of nucleation controlled permanent magnets (J. Appl. Phys. {bold 64}, 6406 and 6416 (1988)), its validity to the problem of Fe-Nd-B type magnets is questioned.
  • Measurements of temperature dependence of the coercive field (H{sub c}) are reported for Nd-Fe-B sintered magnets. The relationship between l{sub g}H{sub c} and 1{sub g}H{sub f} was deduced from the Gaunt's Localized weak pinning model, which can be written as the following form, 1{sub g}H{sub c} = 1{sub g}H{sub f}+1{sub g}25 (31{gamma}b{sup 2}/25kT {minus} 1), where {gamma} is the domain wall energy, b is the range of interaction between domain wall and pin. The values of 1{sub g}H{sub c} were calculated using the above equation, which are in good agreement with the experiments.