Magnetic anisotropy in ultrathin Fe films on GaAs, ZnSe, and Ge (001) substrates

Abstract

We discuss magnetic anisotropy parameters of ferromagnetic body-centered cubic (bcc) Fe films grown by molecular beam epitaxy (MBE) on (001) substrates of face-centered cubic (fcc) GaAs, ZnSe, and Ge. High-quality MBE growth of these metal/semiconductor combinations is made possible by the fortuitous atomic relationship between the bcc Fe and the underlying fcc semiconductor surfaces, resulting in excellent lattice match. Magnetization measurements by superconducting quantum interference device (SQUID) indicate that the Fe films grown on (001) GaAs surfaces are characterized by a very strong uniaxial in-plane anisotropy; those grown on (001) Ge surfaces have a fully cubic anisotropy; and Fe films grown on ZnSe represent an intermediate case between the preceding two combinations. Ferromagnetic resonance measurements carried out on these three systems provide a strikingly clear quantitative picture of the anisotropy parameters, in excellent agreement with the SQUID results. Based on these results, we propose that the observed anisotropy of cubic Fe films grown in this way results from the surface reconstruction of the specific semiconductor substrate on which the Fe film is deposited. These results suggest that, by controlling surface reconstruction of the substrate during the MBE growth, one may be able to engineer the magnetic anisotropy in Fe, and possibly also in other MBE-grown ferromagnetic films.

Ferromagnetic resonance and spin-wave resonances in GaMnAsP films

“…From the evolution of the angular dependence of H R with P concentration, we see that the angular dependence in the top panels changes from a U shape to a Λ shape, eventually evolving into a two-resonance behavior. 12 This behavior can be readily seen from the FMR dispersion fields). The resonance occurs whenever the plotted curves equal ω/γ = 3383 Oe for g = 2.0 and the microwave frequency 9.4 GHz used in this experiment, indicated in the figures by a horizontal dotted line.…”

Magnetic anisotropy of crystalline Fe films grown on (001) GaAs substrates using Ge buffer layers

“…As noted earlier, disappearance of difference between the orthogonal < 110 > directions is due to the use of the Ge buffer, in which the preference of surface reconstruction along specific < 110 > directions is absent. 17,18 However, an interesting new feature of the PHR data is shown in Fig. 2 in the form of shifts of the hysteresis loop centers away from the < 110 > directions, toward the …”

“…Prior to the Fe deposition, an 85 nm Ge buffer was deposited on the GaAs substrate to eliminate the [110] uniaxial anisotropy in the Fe film, known to be related to the reconstruction of As ions on the surface of the GaAs substrate. 17,18 Elimination of the [110] anisotropy makes the Fe films grown in this way more suitable for detecting the relatively weak effects arising from the [100] uniaxial anisotropy. Throughout the deposition of the Fe layer, the reflection high energy electron diffraction (RHEED) showed streaky pattern indicating high quality crystalline growth without any indication of cluster formation.…”

“…Throughout the deposition of the Fe layer, the reflection high energy electron diffraction (RHEED) showed streaky pattern indicating high quality crystalline growth without any indication of cluster formation. 17 A 6 nm Fe film was then grown directly on the Ge buffer, and was finally covered by a thin layer of Au (2 nm) to protect the Fe layer from oxidation.…”

Magnetic properties of Ni films deposited on MBE grown Bi2Se3 layers

“…Indeed, there are quite a number of articles reporting the dependence of the magnetic properties of the ferromagnetic films on the choice of buffer layers and substrates. [3][4][5][6] The use of Bi 2 Se 3 as a buffer layer for the growth of Ni film has special meaning since the Bi 2 Se 3 is a new type of quantum matter called the topological insulator (TI), which shows exotic surface properties originated from the strong spin-orbit coupling effect. [7][8][9][10] It is, therefore, expected that the magnetic property of the ferromagnetic film deposited on the TI surface will be significantly different from that grown on normal semiconductors or insulators.…”