Interfacial Effect in Fe/ InGaAs Magnetism

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The characterization of Ferromagnet / Semiconductor interfaces Fe/In0.5Ga0.5As system has been a topic of great interest because of the possible future development of spintronics, e.g., spin injection through the ferromagnetic thin film to the semiconductor. The morphologies of 4-and 20-nm thick iron layers are shown on Figures 1(a) and 1(b). They clearly highlight differences in roughness and morphology. The 4-nm-thick Fe film looks flat, whereas granular structures features are observed for the higher thickness layer. On the oher hand, we have used both complementary techniques: Vibrating Sample Magnetometer VSM and Vibrating Sample Magnetometer FMR measurements to display how change the magnetic anisotropies as a function of thickness Fe layer at room temperature. This is explained by a competition between interfacial and bulk iron magnetism and increase of the coercive field with thickness. A strong in-plan uniaxial magnetic anisotropy is observed for the 4-nm-thick Fe layer by the existence of magnetic easy and hard axis. Increase in thickness causes a reduction of the uniaxial anisotropy (Fig. 2(b)) prior to its complete disappearance (Figs. 2c and 2d). Figure 3 illustrates the results of measurements of FMR and shows that, at high iron coverage (8 and 20 nm), only one peak is observed. It corresponds to the uniform mode due to the precession of layer magnetization around the applied field. The observed increase of the FMR peak width at higher iron thicknesses is correlated with the number of inhomogeneities in the layer due, for example, to the increase of the roughness. Decreasing the iron thickness makes appear several modes: the 4-nm spectrum shows a double peak structure. These structures are explained by a uniform mode in relation with the iron layer at low field and to an interface mode, respectively. A dependence of the magnetic anisotropies as a function of temperature in Figure 4 show a decrease of perpendicular anisotropies with increasing temperature. The angular dependence of FMR at room temperature RT shown in Figure 5 that the over angular periodicity is 180°.

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Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites
Published: June 21, 2010
Pages: 168 - 171
Industry sector: Advanced Materials & Manufacturing
Topic: Materials Characterization & Imaging
ISBN: 978-1-4398-3401-5