The frequency dependence of the magnetic energy losses in sintered Mn–Zn ferrites is predicted from the quasistatic regime to the megahertz range. The predicting model is based on the appraisal of the contributions by domain wall (dw) displacements and magnetization rotations and the related relaxation-resonant-type dissipation mechanisms. Eddy currents are demonstrated to play little to negligible role. The frequency dependence of the dw generated losses is calculated from knowledge of the quasistatic losses, whereas the contribution by rotations is obtained via the Landau-Lifshitz-Gilbert equation, assuming distributed anisotropy fields. The model excellently applies to the frequency response of commercial ferrites.

An extension of the thin shell formulation for the analysis of the shielding efficiency of multilayered passive shields is presented in the paper. After a validation of the proposed approach by comparison with analytical results in the case of a cylindrical shield placed in a uniform field, the model is applied to the analysis of shielding configurations of practical interest.

Using local scanning electrical techniques we study edge effects in side-gated Hall bar nanodevices made of epitaxial graphene. We demonstrate that lithographically defined edges of the graphene channel exhibit hole conduction within the narrow band of ~60–125 nm width, whereas the bulk of the material is electron doped. The effect is the most pronounced when the influence of atmospheric contamination is minimal. We also show that the electronic properties at the edges can be precisely tuned from hole to electron conduction by using moderate strength electrical fields created by side-gates. However, the central part of the channel remains relatively unaffected by the side-gates and retains the bulk properties of graphene.

This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni₈₀Fe₂₀ antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features.

We compute the classical eddy current losses in soft magnetic composite (SMC) materials, taking into account the eddy current paths appearing at the scale of the sample cross-section because of random contacts between the grains. The prediction of this loss contribution is a challenging task, because of the stochastic nature of the associated conduction process. We start our study from an identification of the statistical properties of the contacts between grains, starting from resistivity measurements. We then develop a numerical loss model for random grain-to-grain conduction, by which we demonstrate that the classical loss in SMCs can be decomposed into a contribution deriving from the eddy currents circulating inside the grains and a contribution due to the macroscopic eddy currents flowing from grain to grain via random contacts. An experimental validation of this model is proposed for a representative SMC material, where the magnetic losses are measured in ring samples with a range of cross-sectional areas.

The domain wall-related change in the anisotropic magnetoresistance in L-shaped permalloy nanowires is measured as a function of the magnitude and orientation of the applied magnetic field. The magnetoresistance curves, compiled into so-called domain wall magnetoresistance state space maps, are used to identify highly reproducible transitions between domain states. Magnetic force microscopy and micromagnetic modelling are correlated with the transport measurements of the devices in order to identify different magnetization states. Analysis allows to determine the optimal working parameters for specific devices, such as the minimal field required to switch magnetization or the most appropriate angle for maximal separation of the pinning/depinning fields. Moreover, the complete state space maps can be used to predict evolution of nanodevices in magnetic field without a need of additional electrical measurements and for repayable initialization of magnetic sensors into a well-specified state.