Onset of ferromagnetism in Fe epitaxially grown on GaAs(001) (4x2) and (2x6)

Citation
F. Bensch et al., Onset of ferromagnetism in Fe epitaxially grown on GaAs(001) (4x2) and (2x6), J APPL PHYS, 89(11), 2001, pp. 7133-7135
Citations number
14
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF APPLIED PHYSICS
ISSN journal
00218979 → ACNP
Volume
89
Issue
11
Year of publication
2001
Part
2
Pages
7133 - 7135
Database
ISI
SICI code
0021-8979(20010601)89:11<7133:OOFIFE>2.0.ZU;2-9
Abstract
Ultrathin Fe films were epitaxially grown at room temperature on GaAs(001) with either predominant (4 x 2) or (2 x 6) surface reconstruction. At nomin al Fe coverages of t(Fe) greater than or equal to 2.8 monolayers (ML), a fe rromagnetic state is observed below a certain critical temperature, T-C. Su rprisingly, the magnetic phase transition at T-C appears even sharper than for Fe films on metallic single-crystal substrates, which were believed to be an excellent representation of two-dimensional (2D) ferromagnets. This m ay be due to the extremely short lateral length scale of film inhomogeneiti es. The critical exponent beta = 0.26 is close to the value expected for 2D XY systems of finite size. For t(Fe) = 3.6 ML, T-C is close to room temper ature. T-C decreases steeply with decreasing Fe coverage, with an average s lope of 270 K/ML. From a power law extrapolation, T-C seems to vanish at t( Fe) = 2.5 ML. The onset of ferromagnetism at t(Fe) = 2.5 ML is interpreted as a percolation phenomenon during the coalescence process of Fe islands. ( C) 2001 American Institute of Physics.