Magnetic properties of two-dimensional arrays of epitaxial Fe (001) submicron particles

Abstract

The magnetic properties of two-dimensional arrays of Fe particles with well-defined geometry, prepared by electron lithography from epitaxial Fe (001) films of thickness of 50 nm, have been studied. Circular particles with diameters of 0.6 and 0.4 μm and rectangular particles 0.9 μm×0.3 μm and 0.7 μm×0.2 μm, were positioned in square and rectangular lattices, respectively, with lattice constants about twice the particle dimensions. Samples were prepared with the lattices oriented along the 〈100〉 and 〈110〉 directions. Hysteresis curves were obtained in the field range ±2 T at temperatures between 30 and 300 K. The hysteresis curves are characteristic for single particles with a multidomain zero-field state. The magnetization and demagnetization processes are mainly governed by the geometrical shape of the particles and their orientation with respect to the crystal directions and the applied field. This implies that the high quality in the epitaxial Fe films is preserved during the patterning process. Magnetic images, obtained by magnetic force microscopy, support the conclusions drawn from the magnetization measurements. The circular particles showed a fourfold symmetry in their magnetic image, which is compatible with the expected domain structure in a disk with cubic crystalline anisotropy.

Domain walls in Fe(001) bicrystals—thickness dependence and field-induced transitions

“…Assuming that this feature may be attributed to ripples, as in polycrystal materials where a weak, directionally fluctuating anisotropy is superimposed on a unidirectional anisotropy, it implies a main magnetisation direction perpendicular to the ripples [2]. This agrees well with the angular relationship of 451 between the easy /1 0 0S directions of the Fe(0 0 1) film and MgO(0 0 1) substrate [3]. MOKE measurements confirmed the expected four-fold symmetry of the in-plane magnetic anisotropy.…”

Self‐organization and finite size effects in epitaxial ferromagnetic MnAs films on GaAs

“…Double hysteresis loops as in Fig. 4a are also observed in studies of the magnetic properties of submicron nanomagnets/disks fabricated by high-resolution electron beam lithography from Supermalloy (Ni 80 Fe 14 Mo 5 ) [23], permalloy [24] and Fe films [25,26]. They are considered to be typical when in disks the magnetic properties are dominated by the creation and annihilation of magnetic-domain walls.…”

Magnetocrystalline and configurational anisotropies in Fe nanostructures

“…In the case of square elements, the magnetization switches between two reversed ''leaf'' states [3] (H is applied along a diagonal). For circular elements of this size, the magnetization is expected to switch between two reversed S-shaped configurations [6]. The lower stability (higher energy) of the ''S'' state with respect to the ''leaf'' one, confirmed by numerical simulations, explains the lower nucleation field observed for circular elements.…”