The finite-temperature magnetism of ultrathin films such as sesquilayer Fe/W(110) and submonolayer Fe/Cu(111) is investigated. Based on renormalizations of Onsager’s exact solution of the two-dimensional Ising model it is shown that superparamagnetism is a common phenomenon in imperfect ultrathin films. The ultimate reason for this behavior is the existence of two structural length scales: the lattice constant, usually considered in renormalization-group theory, and the characteristic size of the film inhomogeneities.
REFERENCES
1.
2.
H. J.
Elmers
, J.
Hauschild
, H.
Höche
, U.
Gradmann
, H.
Bethge
, D.
Heuer
, and U.
Köhler
, Phys. Rev. Lett.
73
, 898
(1994
).3.
D.
Sander
, R.
Skomski
, A.
Enders
, C.
Schmidthals
, and J.
Kirschner
, Phys. Rev. Lett.
77
, 2566
(1996
).4.
Y.
Park
, S.
Adenwalla
, G. P.
Felcher
, and S. D.
Bader
, Phys. Rev. B
52
, 12779
(1995
).5.
R. Skomski, J. Magn. Magn. Mater. (in press).
6.
U. Gradmann, Dreikönigstreffen Bad Honnef, 1996 (unpublished); U. Krey, ibid.
7.
For experimental evidence based on STM micrographs and Kerr hysteresis loops, see J. Shen et al., these proceedings.
8.
L. P.
Kadanoff
, W.
Götze
, D.
Hamblen
, R.
Hecht
, E. A. S.
Lewis
, V. V.
Palciauskas
, M.
Rayl
, J.
Swift
, D.
Aspnes
, and J.
Kane
, Rev. Mod. Phys.
39
, 395
(1967
).9.
D. C. Mattis, The Theory of Magnetism II: Thermodynamics and Statistical Mechanics (Springer, Berlin, 1985).
10.
J. M. Yeomans, Statistical Mechanics of Phase Tansitions (Oxford University Press, Oxford, 1992).
11.
12.
E. Kneller, Ferromagnetismus (Springer, Berlin, 1962).
13.
R.
Skomski
and V.
Christoph
, Phys. Status Solidi B
156
, K149
(1989
).14.
K.-H. Fischer and A. J. Hertz, Spin Glasses (Cambridge University Press, Cambridge, 1991).
15.
16.
17.
18.
This content is only available via PDF.
© 1997 American Institute of Physics.
1997
American Institute of Physics
You do not currently have access to this content.
