We have analyzed the electron transport processes in Al/AlOx/Al junctions. The samples were produced by glow-discharge-assisted oxidation of the bottom electrode. The nonlinear I–V curves of 17 samples were measured at room temperature, being very well fitted using the Simmons’ equation with the insulating barrier thickness, barrier height, and the junction area as free parameters. An exponential growth of the area normalized electrical resistance with thickness is obtained, using just values from I–V curve simulations. The effective tunneling area corresponding to the “hot spots” can be quantified and is five orders of magnitude smaller than the physical area in the studied samples.

Field-dependent transverse permeability characterization of amorphous thin films with nominal composition Fe73.5Cu1Nb3Si13.5B9 was performed for frequencies in the range of 100kHz–1.8GHz. Dynamic and static magnetic properties were investigated in films with thickness in the range from 21to5000nm. Samples with thicknesses below 85nm exhibit a well-defined in-plane uniaxial anisotropy and uniform ferromagnetic resonance modes. Samples thicker than 85nm were found to be magnetically isotropic in the plane, with complex magnetic dynamics depicted by several ferromagnetic resonance modes detected at relatively low fields. The results are discussed in terms of the stress contribution to the magnetic anisotropy of the samples.

We investigate the statistical properties of the Barkhausen noise in amorphous ferromagnetic films with thicknesses in the range between 100 and 1000 nm. From Barkhausen noise time series measured with the traditional inductive technique, we perform a wide statistical analysis and establish the scaling exponents τ , α, 1/σνz, and ϑ. We also focus on the average shape of the avalanches, which gives further indications on the domain wall dynamics. Based on experimental results, we group the amorphous films in a single universality class, characterized by scaling exponents τ ∼ 1.27, α ∼ 1.5, 1/σνz ∼ ϑ ∼ 1.77, values similar to that obtained for several bulk amorphous magnetic materials. Besides, we verify that the avalanche shape depends on the universality class. By considering the theoretical models for the dynamics of a ferromagnetic domain wall driven by an external magnetic field through a disordered medium found in literature, we interpret the results and identify an experimental evidence that these amorphous films, within this thickness range, present a typical three-dimensional magnetic behavior with predominant short-range elastic interactions governing the domain wall dynamics. Moreover, we provide experimental support for the validity of a general scaling form for the average avalanche shape for non-mean-field systems.

In this work, the magnetization dynamics of soft magnetic materials is studied with the aid of transverse differential permeability (I ac , f ,H dc ) spectra. Contributions to the magnetization processes from domain wall motion and rotation of the magnetization can be extracted from the transverse differential permeability data which are in turn obtained from impedance Z(I ac , f ,H dc ) spectra. In particular, an iteration method is used to extract (I ac , f ,H dc ) from Z(I ac , f ,H dc ) data. The approach is tested in samples with a very well known domain structure, namely (110)͓001͔FeSi 3% . Permeability spectra (I ac , f ,H dc ) were obtained in the frequency range (100 Hzр f р100 kHz), probe current range (0.1рI ac р50 mA) and dc magnetizing field range (0рH dc р500 Oe). It is shown that the method developed in this article can be efficiently used to identify and study different dynamic processes driven by the probe current and controlled by the external dc field. In particular, it is shown that the method provides the tools to separate the reversible and irreversible parts of these processes.