Abnormal near-surface magnetic properties of heterogeneous (amorphous/nanocrystalline) Fe80.5Nb7B12.5 ribbons

The study of near-surface and volume magnetic properties and also near-surface micromagnetic structure (equilibrium distribution magnetization) of the as-cast and annealed for 1 h at T = 380–650 °C Fe80.5Nb7B12.5 ribbons was carried out employing magneto-optical micromagnetometer and a vibrating sample magnetometer (VSM). According to VSM data, the annealed at T ≤ 600 °C samples exhibit a slight in-plane magnetic anisotropy and excellent soft magnetic properties. For the annealed at T = 400–550 °C ribbons, inverted near-surface hysteresis loops were discovered that was ascribed to the coexistence of amorphous and nanocrystalline phases. The study of near-surface micromagnetic structure of the ribbons showed that with increasing annealing temperature, the magnetic homogeneity of the examined samples improves.