We report a universal dependence of switching field of patterned magnetic nanolines as a function of the linewidth for Co and NiFe films of various thicknesses. This dependence is shown to be consistent with a nucleation picture in which the magnetization reversal is controlled only by a small nucleus equivalent to a particle with an aspect ratio of 1.25, which spreads across the width of the nanoline. Micromagnetic simulation, taking into account of the edge roughness, agrees well with the observed results.

The authors investigate the rectified motion of vortices in superconducting films deposited on top of a close-packed array of open in-plane magnetized triangular micromagnets. The dc voltage induced by the vortex drift under an ac excitation is recorded for three different magnetic configurations of the triangles. When the magnetic elements are in the as-grown state a rectification signal which reverses sign when the field changes polarity is observed. In contrast to that, when the array of triangles is magnetized the observed rectification effect is independent of the field polarity and can be reverted by reorienting the magnetization of the micromagnets.

To better understand the response of domain walls to current induced spin transfer torques, we have directly imaged the internal magnetic structure of domain walls in current-carrying ferromagnetic nanostripes. Domain wall images were acquired both while a constant current was flowing through the wire, and after applying current pulses. Domain walls ranging from vortices in wide (1 m) wires, to transverse walls in narrow (100 nm) wires were quantitatively analyzed using scanning electron microscopy with polarization analysis (SEMPA). The domain wall motion is characterized by strong interactions with random pinning sites along the wire. The walls either jump with the electron flow between pinning sites, or the pinned walls are distorted by the current. The domain wall propagation is also associated with transverse motion of the vortex core.

Articles you may be interested inDevelopment of magnetoresistive thin film sensor for magnetic field sensing applications AIP Conf. Proc. 1512, 30 (2013); 10.1063/1.4790897 Domain wall displacement in Py square ring for single nanometric magnetic bead detection Magnetism in zigzag-shaped thin-film elements is investigated using scanning electron microscopy with polarization analysis, magnetotransport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length of the element, and is strongly correlated to the corrugated edges. We show that this simple and unique geometry can be used as a single-axis magnetic field sensor. In this configuration, the sensors are primarily sensitive to fields parallel to the applied current. Our results can be interpreted in terms of a coherent rotation model of the magnetization. These devices are scalable to nanometer dimensions.

We have successfully demonstrated the construction of patterned magnetic nanostructures down to 50 nm dimensions using electron-beam lithography. Two types of patterned structures have been fabricated for this work: nanostructured arrays consisting of isolated identical elements and nanostructured chains of alternating elements with different widths. Small patterned arrays (∼200 μm×200 μm) have been characterized using a variable temperature (5 to 325 K) focused magneto-optic Kerr effect (MOKE) measurement system. The switching field of the isolated element arrays is found to be inversely proportional to the element width. However, as the elements of two different widths are connected to form a chain, magnetization reversal is essentially controlled by the wider constituent, indicating that the switching of chains starts in the wider elements. Domain walls in these wide elements then propagate through the narrower components, requiring a lower field than domain nucleation in the narrow elements. Magnetic force microscopy (MFM) images show that in the virgin state the narrower elements are domain wall free but complex domain patterns exist in the wider elements. Both field-dependent MFM imaging and micromagnetic simulations agree very well with the MOKE measurements.