The thickness and aspect ratio dependence of magnetic domain formation in CoFe nanolayer patterns on GaAs (001) substrates are investigated by means of a direct approach using magnetic force microscopy at room temperature. Magnetic force microscope observations under as‐deposition condition show that magnetic domain formation in the patterns depends strongly on the aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates. A single magnetic domain is more easily formed in the patterns with a higher aspect ratio, with a thinner nanolayer thickness, and along the ⟨110⟩ direction of the substrates. The magnetic fields are next applied in the direction parallel to the ⟨1–10⟩ and ⟨110⟩ orientations of the substrates to characterize a magnetization switching behavior in the patterns. The aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates strongly affect the magnetic fields needed for magnetization switching in the patterns. A higher magnetic field is required for a higher aspect ratio and a thinner nanolayer thickness of the patterns. All the direct observations confirm that the magnetic domain structures and magnetization switching are tuned by controlling aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates.

We study the magnetotransport properties of single InAs nanowires grown by selective-area metal–organic vapor-phase epitaxy. The semiconducting InAs nanowires exhibit a large positive ordinary magnetoresistance effect. However, a deviation from the corresponding quadratic behavior is observed for an orientation of the applied magnetic field perpendicular to the nanowire axis. This additional contribution to the magnetoresistance can be explained by diffuse boundary scattering of free carriers in the InAs nanowire and results in a reduction of the charge carrier mobility. As a consequence, angle-dependent magnetotransport measurements reveal a highly anomalous behavior. Numerical simulations have been conducted to further investigate the effect of classical boundary scattering in the nanowires. On the basis of the numerical simulations, an empirical description is derived, which yields excellent agreement with the experimental data and allows one to quantify the contribution of boundary scattering to the magnetoresistance effect.

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Semiconducting nanowires hold great interest as building blocks for nanoscaled electronic and optoelectronic devices, such as field-effect transistors, gas sensors, and light-emitting diodes. Due to their unique structural properties, with a high surface-to-volume ratio and quasi-one-dimensionality, they exhibit interesting new optical and electronic properties. As device performance strongly depends on charge carrier density, carrier lifetime, and carrier mobility, detailed knowledge of the transport properties in quasi-one-dimensional nanostructures is essential. In particular, InAs nanowires are of considerable interest for high-performance transistors, thermoelectrics, spintronics, and quantum computing devices as they not only exhibit high carrier mobility but also a strong spin–orbit coupling and a large g-factor. Furthermore, at low temperatures a surface accumulation layer can occur in InAs nanowires after surface treatments, resulting in interesting mesoscopic transport phenomena such as universal conductance fluctuations or weak antilocalisation. However, for nanoscaled magnetoelectronic or spintronic applications, nanowires with adjustable ferromagnetic properties are desirable. As the growth of dilute magnetic semiconductors and semiconducting nanowires with a Curie temperature above 300 K is still challenging, MnAs/InAs heterojunction nanowires, where ferromagnetic nanoclusters are embedded in a semiconducting matrix, may represent a promising alternative. Additionally, such heterojunction nanowires have been reported to exhibit huge magnetoresistance effects as well as a relatively long spin-relaxation time.