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Giant magnetoresistance (GMR) effects up to 10% have been observed in Co/Cu/FeNi spin valve structures grown onto step bunched vicinal Si(111) substrates misoriented towards [11-2]. The step bunching is activated using a simple thermal treatment which leads to surfaces where terraces alternate with facets at the nanometer scale. GMR of the spin valve structures is investigated with the current applied parallel or perpendicular to the steps. An in-plane uniaxial magnetic anisotropy is induced in each magnetic layer with the easy axis parallel to the steps. This results in square GMR behavior when the field is applied along the easy axis. Specific features observed when the field is applied along the hard axis are also shown to be the consequence of this anisotropy. When the initial misorientation angle of the substrate becomes higher than 4°, we observe an enhancement of the room-temperature GMR when the current is applied perpendicular to the steps. The origin of this enhancement is discussed based on the...

High-quality thin-film of NiMnSb with the Clb crystal structure can be grown by low-power sputtering, at substrate temperatures as low as 250 °C. Structural and magneto-optical properties of these films are similar to those of bulk material prepared at high temperatures, which suggest that the predicted 100% spin-polarized behavior of NiMbSb may also be found in these films. The magneto-optical Kerr spectra have been measured, and they are found to be very sensitive to the preparation condition. The spectrum of the bulk alloy is closely reproduced only in the case of optimized films. This suggests that, in the optimized case, the electronic band structure is bulklike.

Magnetic thin films have been deposited by molecular beam epitaxy on vicinal Si(111) substrates misoriented towards [11‐2]. The substrates were thermally pretreated in order to activate the step bunching mechanism, which results in a laterally modulated surface topology with a period of ∼800 A. Cobalt or permalloy layers grown on such surfaces exhibit an in‐plane uniaxial magnetic anisotropy. This anisotropy is associated with the lateral pseudoperiodic variation of the crystalline orientation of the metallic layers as observed by transmission electron microscopy. Magnetoresistance measurements on microstructured films reveal a single‐domain behavior with a magnetization reversal by rotation.

NixFe100−x thin films with x≊65%–90%, have been grown by molecular beam epitaxy on top of thin Fe/Pd multilayers. In situ electron diffraction, and ex situ x‐ray diffraction indicate epitaxial growth of the films in a face‐centered cubic structure, with the (011) axis perpendicular to the substrate. This has been confirmed by electron microscopy, which also reveals regions of polycrystalline growth. Although the permalloy film itself has negligible magnetic anisotropy, the in‐plane uniaxial anisotropy induced in the Fe layers can be transferred to the NiFe alloy layer through a 5‐A Pd spacer layer. The high crystalline quality of the films results in bulklike transport properties; σ=25 μΩ cm, and ΔR/R=2%, for a 60‐A‐thick film.

Photoluminescence experiments have been carried out on erbium doped Ga0.55Al0.45As under continuous wave and pulsed laser excitation. For the first time the emissions arising from the two first Er3+ excited states 4I11/2, 4I13/2 and their temperature dependence have been systematically studied. From these results the nature and the excitation‐deexcitation processes of these photoluminescences are discussed. With the help of these spectroscopic data we give an estimate of the stimulated emission cross section and the laser applications of such rare‐earth doped III‐V materials are examined.

Zn1−xMnxO diluted magnetic semiconductor single phase thin films have been grown by the MOCVD technique. Depositions have been done on fused silica and (0001)-sapphire substrates. Layers on silica are polycrystalline with [001] preferential orientation, while Zn1−xMnxO films on c-sapphire are highly (0001) textured. Manganese content (x) in the samples varies in 0.00–0.44 range. Change of c lattice parameter follows Vegard’s law. Hall effect measurements show a decrease of mobility with Mn increase and no change of carrier concentration. Optical transmission results present the increase of band gap with manganese incorporation. Superconducting quantum interference device magnetometry shows Curie–Weiss behaviors of the susceptibility with antiferromagnetic coupling with an effective exchange constant of J1∕kB=−16K.

49th Annual Conference on Magnetism and Magnetic Materials, Jacksonville, FL, NOV 07-11, 2004; International audience; Zn1-xMnxO layers with x varying between 0.006 and 0.22, have been prepared by metal-organic chemical-vapor deposition technique and analyzed by electron paramagnetic 2, resonance spectroscopy. The layers show an exchange narrowed single line spectrum of Mn2+ ions; its temperature dependence demonstrates antiferromagnetic coupling with an effective exchange constant of J1/k(B)=-14.9 K. (c) 2005 American Institute of Physics.