Abstract
Different magnetic anisotropies and magnetization reversal mechanisms were identified in magnetic nano-objects of four-fold symmetry, using micromagnetic simulations. Nano-particles with lateral dimensions between 50 nm and 400 nm, simulated with typical properties of permalloy, iron and cobalt, were tested in dependence of the angular orientation with respect to the externally applied magnetic field. All nano-objects exhibited steps on the sides of the hysteresis loops, which can be correlated with stable intermediate states at remanence, for some angular regions. Coercive fields were found to show an irregular and unpredictable angular dependence in case of cobalt nano-particles, while this material depicted the largest number of steps in general. Comparing the angular dependence of the coercive fields with previous calculations, it was shown that usual descriptions of fourfold anisotropies are no longer valid in most of the nano-objects under examination.
Highlights
Different magnetic anisotropies and magnetization reversal mechanisms were identified in magnetic nano-objects of four-fold symmetry, using micromagnetic simulations
All nanoobjects exhibited steps on the sides of the hysteresis loops, which can be correlated with stable intermediate states at remanence, for some angular regions
Different numbers of steps on the sides of the hysteresis loops were found, some of which are correlated with stable intermediate states at remanence
Summary
Nanostructured magnetic particles have been examined theoretically and experimentally during the last two decades due to their possible applications as sensors or magnetic storage media.[1,2,3] Correlated with the advances in lithographic techniques,[4,5,6,7,8,9] magnetic nanostructures can become smaller and smaller, with size and geometric details being controlled, allowing for tailoring the magnetic properties of the structures by tuning their shapes. Among the special geometries which have recently attracted much interest in the development of advanced technological application, such as magnetic sensors, there are nanostrips, and nanowires, exhibiting three or only two geometric parameters to be controlled, respectively, which define their magnetic properties.[10,11,12,13,14]. 0.5 d (nm) fields as well as shape anisotropies in such structures of dimensions reduced to nanoscale, different overall magnetic anisotropies can be expected to occur which cannot be described by common phenomenological or macroscopic approaches,[18,19] resulting in unusual magnetic states and magnetization reversal processes
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