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This work studies the influence of crystallographic alignment onto magnetization reversal in partially epitaxial Co films. A reproducible growth sequence was devised that allows for the continuous tuning of grain orientation disorder in Co films with uniaxial in-plane anisotropy by the controlled partial suppression of epitaxy. While all stable or meta-stable magnetization states occurring during a magnetic field cycle exhibit a uniform magnetization for fully epitaxial samples, non-uniform states appear for samples with sufficiently high grain orientation disorder. Simultaneously with the occurrence of stable domain states during the magnetization reversal, we observe a qualitative change of the applied field angle dependence of the coercive field. Upon increasing the grain orientation disorder, we observe a disappearance of transient domain wall propagation as the dominating reversal process, which is characterized by an increase of the coercive field for applied field angles away from the easy axis for well-ordered epitaxial samples. Upon reaching a certain disorder threshold level, we also find an anomalous magnetization reversal, which is characterized by a non-monotonic behavior of the remanent magnetization and coercive field as a function of the applied field angle in the vicinity of the nominal hard axis. This anomaly is a collective reversal mode that is caused by disorder-induced frustration and it can be qualitatively and even quantitatively explained by means of a two Stoner-Wohlfarth particle model. Its predictions are furthermore corroborated by Kerr microscopy and by Brillouin light scattering measurements. [ABSTRACT FROM AUTHOR]

The surface morphology, crystal structure, and in-plane magnetic anisotropy of sputter deposited Co70Fe30 films on GaAs(110) epilayer substrates have been investigated. The surface morphology of thin Co70Fe30 films appears to closely follow that of the underlying GaAs(110) substrate. The study of the crystal structure by x-ray diffraction shows that no crystallographic orientation other than Co70Fe30(110) is present in our films, although we cannot unambiguously deconvolute characteristic reflections of Co70Fe30(110) from those of GaAs(110) due to the very small lattice mismatch. High-resolution transmission electron microscopy shows that the crystal structure of the Co70Fe30 film is coherently matched to the GaAs(110) substrate. The magnetic anisotropies in both 35 and 1100 Å thick films are consistent with those of similar epitaxial films, and demonstrate that a strong bcc (110) texture is propagated throughout the entire film thickness. The cubic and uniaxial anisotropy constants extracted by fitting with the Stoner–Wohlfarth model are consistent with those of molecular beam epitaxy grown bcc CoxFe(100-x)/GaAs(110). This work shows that sputter deposition may be used to produce structurally coherent bcc-Co70Fe30/GaAs(110) contacts suitable for spin-injection applications. [ABSTRACT FROM AUTHOR]

In order to optimize their magnetic properties, Fe/Au multilayers were treated by pregrowth and postgrowth ion-beam bombardments. The ferromagnetic resonance linewidth was used as our main figure of merit. The pregrowth treatment of the MgO substrate using a 60 eV atomic oxygen beam resulted in a reduction of the inhomogeneous linewidth broadening in comparison with a sample grown on an untreated substrate. This homogeneity increase is linked to the removal of substrate carbon contamination by the chemically active oxygen. It correlates with the reduced interface roughness. The postgrowth sample irradiation using 30 keV He+ ions also reduces the inhomogeneous broadening in the linewidth. Fe and Au have a miscibility gap, but the demixing is kinetically quenched at room temperature. Ion collisions locally minimize the interface energy by providing the energy necessary for localized demixing, resulting in a smoothing effect. Combined, the pregrowth and the postgrowth irradiations lead to the lowest observed linewidth. [ABSTRACT FROM AUTHOR]

We present a modification of the magnetization and an electronic reconfiguration due to interfacial coupling between strain relaxed La0.66Ca0.34MnO3 and ultrathin BaTiO3 films using the magnetocaloric effect and photoemission electron microscopy at the Mn, Ti L 2, 3 edges. The addition of a top BaTiO3 layer leads to strain-induced enhancement of the magnetocaloric effect in La0.66Ca0.34MnO3, due to the structural transitions in BaTiO3, and to room temperature ferromagnetism due to electronic reconfiguration at the interface. [ABSTRACT FROM AUTHOR]

We have studied thin film samples of FeSi and MnSi with different degrees of chemical ordering using the time-resolved magneto-optical Kerr effect to elucidate the influence of defects in the crystal structure on magnetization dynamics. Surprisingly, we find that the presence of defects does not influence the optically induced magnetization dynamics on the ultrashort timescale (some 100 fs). However, we observe a second demagnetization stage with a timescale of tens of picoseconds in MnSi for low chemical ordering; that is, a large number of defects. We interpret this second demagnetization step as originating from scattering of mostly thermalized majority electrons into unoccupied minority defect states. [ABSTRACT FROM AUTHOR]

Epitaxial CoRu-alloy films with (1010) surface orientation and varying stoichiometry have been grown at room temperature. In order to achieve good epitaxy independent from the alloy composition, we have devised an underlayer sequence, which utilized a CrRu-alloy film as template layer with individually optimized composition. All alloys in the composition range of 0-30 at. % Ru content exhibit hcp structure and thus uniaxial magneto-crystalline anisotropy. We observe an almost linear decrease of the saturation magnetization and Curie temperature with increasing Ru content. However, the magneto-crystalline anisotropy shows a non-monotonous behavior with a maximum near 15% Ru. [ABSTRACT FROM AUTHOR]