Estudo dos efeitos do desalinhamento nos eixos de anisotropia em curvas de magnetoimpedância para sistemas de NiFe/FeMn com exchange bias

Abstract

Magnetic systems that present the exchange bias (EB) phenomenon continue to attract the attention of many studies, which aim to improve technological applications and phenomenological description. Magnetoimpedance (MI) is a tool that can be used in the magnetic characterization of materials and it is also the physical phenomenon that is the basis of many magnetic sensors. In this work was sought to develop a calculation routine with the purpose of evaluating the behavior of magnetoimpedance in systems with EB in the most diverse situations. With it, it was possible to investigate the influence of the main parameters, both of the sample and the experiment itself, on the MI curve. It was possible to verify, for example, that the misalignment of the uniaxial and unidirectional anisotropy axes is a possible source of asymmetry in the amplitude of the magnetoimpedance peaks, a factor little explored in other studies. For asymmetry to occur, both anisotropies must be misaligned from the DC field. By investigating the evolution of the asymmetry with the measurement frequency, it was possible to separate the asymmetry generated by the misalignment of the DC field from that generated by the misalignment of the anisotropies. This different behavior made it possible to propose two experimental configurations that would make it possible to evaluate the occurence of misalignment between the anisotropy axes. Finally, adjustments were made to the MI experimental data for Ni81Fe19 /FeMn samples.