Onset of ferromagnetism in Fe epitaxially grown on GaAs(001) (4{times}2) and (2{times}6)
Ultrathin Fe films were epitaxially grown at room temperature on GaAs(001) with either predominant (4{times}2) or (2{times}6) surface reconstruction. At nominal Fe coverages of t{sub Fe}{ge}2.8 monolayers (ML), a ferromagnetic state is observed below a certain critical temperature, T{sub C}. Surprisingly, the magnetic phase transition at T{sub 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 may be due to the extremely short lateral length scale of film inhomogeneities. The critical exponent {beta}=0.26 is close to the value expected for 2D XY systems of finite size. For t{sub Fe}=3.6ML, T{sub C} is close to room temperature. T{sub C} decreases steeply with decreasing Fe coverage, with an average slope of 270 K/ML. From a power law extrapolation, T{sub C} seems to vanish at t{sub Fe}=2.5ML. The onset of ferromagnetism at t{sub Fe}=2.5ML is interpreted as a percolation phenomenon during the coalescence process of Fe islands. {copyright} 2001 American Institute of Physics.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40203980
- Journal Information:
- Journal of Applied Physics, Vol. 89, Issue 11; Other Information: DOI: 10.1063/1.1361258; Othernumber: JAPIAU000089000011007133000001; 463111MMM; PBD: 1 Jun 2001; ISSN 0021-8979
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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