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Title: Simulation of alnico coercivity

Abstract

Micromagnetic simulations of alnico show substantial deviations from Stoner-Wohlfarth behavior due to the unique size and spatial distribution of the rod-like Fe-Co phase formed during spinodal decomposition in an external magnetic field. Furthemore, the maximum coercivity is limited by single-rod effects, especially deviations from ellipsoidal shape, and by interactions between the rods. In both the exchange interaction between connected rods and magnetostatic we consider the interaction between rods, and the results of our calculations show good agreement with recent experiments. Unlike systems dominated by magnetocrystalline anisotropy, coercivity in alnico is highly dependent on size, shape, and geometric distribution of the Fe-Co phase, all factors that can be tuned with appropriate chemistry and thermal-magnetic annealing.

Authors:
 [1];  [2];  [3];  [1];  [1]; ORCiD logo [4];  [1];  [1];  [1]
  1. Ames Lab., Ames, IA (United States)
  2. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy
  3. 1137 W. Emerald Ave., Mesa, AZ (United States)
  4. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Dept. of Materials Science and Engineering
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1371888
Alternate Identifier(s):
OSTI ID: 1369083
Report Number(s):
IS-J-9371
Journal ID: ISSN 0003-6951
Grant/Contract Number:
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 111; Journal Issue: 2; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE

Citation Formats

Ke, Liqin, Skomski, Ralph, Hoffmann, Todd D., Zhou, Lin, Tang, Wei, Johnson, Duane D., Kramer, Matthew J., Anderson, Iver E., and Wang, C. -Z. Simulation of alnico coercivity. United States: N. p., 2017. Web. doi:10.1063/1.4992787.
Ke, Liqin, Skomski, Ralph, Hoffmann, Todd D., Zhou, Lin, Tang, Wei, Johnson, Duane D., Kramer, Matthew J., Anderson, Iver E., & Wang, C. -Z. Simulation of alnico coercivity. United States. doi:10.1063/1.4992787.
Ke, Liqin, Skomski, Ralph, Hoffmann, Todd D., Zhou, Lin, Tang, Wei, Johnson, Duane D., Kramer, Matthew J., Anderson, Iver E., and Wang, C. -Z. Mon . "Simulation of alnico coercivity". United States. doi:10.1063/1.4992787.
@article{osti_1371888,
title = {Simulation of alnico coercivity},
author = {Ke, Liqin and Skomski, Ralph and Hoffmann, Todd D. and Zhou, Lin and Tang, Wei and Johnson, Duane D. and Kramer, Matthew J. and Anderson, Iver E. and Wang, C. -Z.},
abstractNote = {Micromagnetic simulations of alnico show substantial deviations from Stoner-Wohlfarth behavior due to the unique size and spatial distribution of the rod-like Fe-Co phase formed during spinodal decomposition in an external magnetic field. Furthemore, the maximum coercivity is limited by single-rod effects, especially deviations from ellipsoidal shape, and by interactions between the rods. In both the exchange interaction between connected rods and magnetostatic we consider the interaction between rods, and the results of our calculations show good agreement with recent experiments. Unlike systems dominated by magnetocrystalline anisotropy, coercivity in alnico is highly dependent on size, shape, and geometric distribution of the Fe-Co phase, all factors that can be tuned with appropriate chemistry and thermal-magnetic annealing.},
doi = {10.1063/1.4992787},
journal = {Applied Physics Letters},
number = 2,
volume = 111,
place = {United States},
year = {Mon Jul 10 00:00:00 EDT 2017},
month = {Mon Jul 10 00:00:00 EDT 2017}
}

Journal Article:
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  • The concerns about the supply and resource of rare earth (RE) metals have generated a lot of interests in searching for high performance RE-free permanent magnets. Alnico alloys are traditional non-RE permanent magnets and have received much attention recently due their good performance at high temperature. In this paper, we develop an accurate and efficient cluster expansion energy model for alnico 5–7. Monte Carlo simulations using the cluster expansion method are performed to investigate the structure of alnico 5–7 at atomistic and nano scales. The alnico 5–7 master alloy is found to decompose into FeCo-rich and NiAl-rich phases at lowmore » temperature. The boundary between these two phases is quite sharp (∼2 nm) for a wide range of temperature. The compositions of the main constituents in these two phases become higher when the temperature gets lower. Both FeCo-rich and NiAl-rich phases are in B2 ordering with Fe and Al on α-site and Ni and Co on β-site. The degree of order of the NiAl-rich phase is much higher than that of the FeCo-rich phase. A small magnetic moment is also observed in NiAl-rich phase but the moment reduces as the temperature is lowered, implying that the magnetic properties of alnico 5–7 could be improved by lowering annealing temperature to diminish the magnetism in NiAl-rich phase. The results from our Monte Carlo simulations are consistent with available experimental results.« less
  • The concerns about the supply and resource of rare earth (RE) metals have generated a lot of interests in searching for high performance RE-free permanent magnets. Alnico alloys are traditional non-RE permanent magnets and have received much attention recently due their good performance at high temperature. In this paper, we develop an accurate and efficient cluster expansion energy model for alnico 5–7. Monte Carlo simulations using the cluster expansion method are performed to investigate the structure of alnico 5–7 at atomistic and nano scales. The alnico 5–7 master alloy is found to decompose into FeCo-rich and NiAl-rich phases at lowmore » temperature. The boundary between these two phases is quite sharp (~2 nm) for a wide range of temperature. The compositions of the main constituents in these two phases become higher when the temperature gets lower. Both FeCo-rich and NiAl-rich phases are in B2 ordering with Fe and Al on α-site and Ni and Co on β-site. The degree of order of the NiAl-rich phase is much higher than that of the FeCo-rich phase. In addition, a small magnetic moment is also observed in NiAl-rich phase but the moment reduces as the temperature is lowered, implying that the magnetic properties of alnico 5–7 could be improved by lowering annealing temperature to diminish the magnetism in NiAl-rich phase. Furthermore, the results from our Monte Carlo simulations are consistent with available experimental results.« less