The energy product (BH)max is a figure of merit quantifying the maximum amount of useful work that can be performed by the magnet. The energy product is determined by the magnetic remanence and the coercivity which, as extrinsic properties, are determined by the magnets’ microstructure. Thus, in principle, magnetic material microstructures may be tailored to obtain defined parameters to produce optimal permanent magnets. However, as asserted by the eponymous Murphy, “Nature favors the hidden flaw”. While there is still much undeveloped potential in nanomagnetic materials, with relevant length scales on the order of 100 Å, accumulating evidence strongly suggests that maximum remanence and maximum coercivity are mutually exclusive in nanocrystalline magnetic materials. Diverse experimental and computational results obtained from nanocrystalline Nd2Fe14B-based magnets produced by melt-spinning techniques and subjected to various degrees of thermomechanical deformation confirm this conclusion. Recent results obtained from temperature-dependent magnetic measurement, magnetic force microscopy and simple micromagnetic modeling will be reviewed and summarized. The results, while somewhat discouraging, do hint at possible materials design routes to sidestep the inherent performance limitations of the magnetic nanostructures.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
C. D. Fuerst and E. G. Brewer, J. Appl. Phys. 73 (1993) 5751.
H. A. Davies, J. Magn. Magn. Mater. 157/158 11 (1996).
E. C. Stoner and E. P. Wohlfarth, Philos. Trans. Roy. Soc. London A 240 (1948) 599.
E. J. Kondorsky, J. Exp. Theor. Fiz. 10 (1940) 420.
D. Givord and M. F. Rossignol, “Coercivity” Ch. 5 in Rare-earth Iron Permanent Magnets, J. M. D. Coey, Ed., Clarendon Press, Oxford (1996).
L. H. Lewis, T. R. Thurston, V. Panchanathan, U. Wildgruber and D. O. Welch, J. Appl. Phys. 82 (7) (1997) 3430.
H. Kronmüller and T. Schrefl, J. Magn. Magn. Mater., 129 (1994) 66.
Giselher Herzer, Materials Science and Engineering A133 (1991) 1.
R. C. O’Handley, Modern Magnetic Materials, John Wiley & Sons, New York (2000) 294.
J. M. D. Coey, “Introduction” Ch. 1 in Rare-earth Iron Permanent Magnets, J. M. D. Coey, Ed., Clarendon Press, Oxford (1996).
D. C. Crew, L. H. Lewis and V. Panchanathan, J. Magn. Magn. Mater. 223 (3) (2001) 261.
D.C. Crew, L.H. Lewis and V. Panchanathan, J. Magn. Magn. Mater. in press.
D. C. Crew and L. H. Lewis, IEEE Trans. Magn. in press.
W.F. Brown, Rev. Mod. Phys. 17 (1945) 15.
A. Aharoni, Rev. Mod. Phys. 34 (1962) 227.
S. Hirosawa and Y. Tsubokawa, J. Magn. Magn. Mater. 84 (1990) 309.
R. Grossinger, X.K. Sun, R. Eibler, K.H.J. Buschow and H.R. Kirchmayr, J. Magn. Magn. Mater. 58 (1986) 55.
D. C. Crew, L. H. Lewis, D. O. Welch, V. Panchanathan, J. Appl. Phys. 87 (2000) 6571.
T. Schrefl, J. Fidler and H. Kronmüller, Phys. Rev. B 49 (9) (1994) 6100.
M. K. Griffiths, J. E. L. Bishop, J. W. Tucker and H. A. Davies, J. Magn. Magn. Mater. 183 (1998) 49.
M. J. Donohue and D. G. Porter <URL: http://math.nist.gov/oommf/> version 1.1.
T. Schrefl, H. F. Schmidts, J. Fidler, H. Kronmüller, J. Appl. Phys. 73 (1993) 6510–6512.
About this article
Cite this article
Lewis, L.H., Crew, D.C. The Coercivity - Remanence Tradeoff in Nanocrystalline Permanent Magnets. MRS Online Proceedings Library 703, 28 (2001). https://doi.org/10.1557/PROC-703-U2.8