Four-fold magnetic anisotropy in a Co film on MgO(001)

Abstract

a b s t r a c tThe development of devices based on magnetic tunnel junctions has raised new interests on the structural and magnetic properties of the interface Co/MgO. In this context, we have grown ultrathin Co films ( r 30Å) by molecular-beam epitaxy on MgO(0 0 1) substrates kept at different temperatures (T S ). Their structural and magnetic properties were correlated and discussed in the context of distinct magnetic anisotropies for Co phases reported in the literature. The sample characterization has been done by reflection high energy electron diffraction, magneto-optical Kerr effect and ferromagnetic resonance. The main focus of the work is on a sample deposited at T S ¼ 25 1C, as its particular way of growth has enabled a bct Co structure to settle on the substrate, where it is not normally obtained without specific seed layers. This sample presented the best crystallinity, softer magnetic properties and a four-fold in-plane magnetic anisotropy with Co/1 1 0S easy directions. Concerning the samples prepared at T S ¼ 200 and 5001 C, they show fcc and polycrystalline structures, respectively and more intricate magnetic anisotropy patterns.

Magnetic Anisotropy of Epitaxially Grown Fe/Mn/Co Trilayers

“…More specifically, the fittings of the angular dependence measurements with the appropriate equilibrium and resonance conditions discussed above yield the anisotropy constants, effective magnetizations, and g-factors listed in Table I. It should be first emphasized that the magnetic anisotropy results are in good agreement with known values for monocrystalline thin Fe [3], [7], [10], [12] and Co [13] films reported in literature. In addition, for films with thin Mn spacer, the Co magnetic anisotropy is slightly higher than that of Fe, but both Fe and Co have a comparable order of magnitude due to their bcc-like features, as suggested by RHEED and XRD data.…”

Room Temperature Exchange Bias in BiFeO3/Co–Fe Bilayers

“…The squareness shows a pronounced unidirectional anisotropy with a superimposed fourfold anisotropy. This indicates that the BiFeO 3 film induces a bct structure in the Co films [16]. The corresponding coercive field versus rotational angle (see Fig.…”

Manipulation of Magnetic Properties and Magnetoresistance in Co/Cu/γ′-Fe4N/Mica Flexible Spin Valves via External Mechanical Strains

“…By a comparison of the M – H curves of flexible SPVs with various t Co values (Figure S6o), the H c value of the Co layer increases with a decrease in t Co and the peak of the M – H curve is not sharp, which indicates that the magnetic anisotropy of flexible SPVs with t Co = 2.4 nm changes. Ultrathin Co films show a 4-fold magnetic anisotropy . Therefore, the magnetization misalignments between Co and γ′-Fe 4 N layers also contribute to the appearance of a positive MR due to the altered magnetic anisotropy.…”