Neutron irradiation effect on permeability and magnetoimpedance of amorphous and nanocrystalline magnetic materials

In this paper we provide physical insights into the effect of neutron irradiation on permeability spectra and magnetoimpedance of amorphous and nanocrystalline alloys. Experimental results indicate that neutron irradiation increases the permeability of the amorphous alloy but decreases the permeability of the nanocrystalline alloy in a high frequency region (f≥1 MHz), while the opposite is found in a low frequency region (f<1 MHz). A careful examination of sample temperature during neutron irradiation process excludes thermal annealing as a possible origin of the observed irradiation effect. The magnetic relaxations in the low and high frequency regions are ascribed to the irreversible domain wall motion and reversible rotational magnetization, respectively. The enhancement in the permeability of the amorphous alloy upon neutron irradiation leads to a parallel improvement of magnetoimpedance response of the material, which is of practical use for sensing applications.