Analysis of hysteretic behavior in a FeCoB-based nanocrystalline alloy by a Preisach distribution and electron holography

Abstract

First order reverse curves have been used to investigate the Preisach distribution and electron holography to observe the spatial variation of the magnetization in Fe40Co40Nb4B13Ge2Cu1 nanocomposite alloys after annealing at 500, 550, 610, and 960°C for 1h. Grain sizes observed for these annealing temperatures varied from 10to200nm. The Preisach distribution reveals that the magnetization process in the sample annealed at 500°C for 1h was dominated by reversible processes, consistent with a small coercivity and mobile domain walls in an external field. At higher annealing temperatures, the irreversible magnetization processes became dominant with increasing grain size. Electron holography observations of the domains show that, for the sample annealed at 500°C, the magnetic flux distribution was uniform with few pinning barriers to domain wall motion consistent with reversible magnetization. The sample annealed at 610°C exhibited irregularity in the shape of magnetic flux lines attributed to the inhomogeneous magnetization distribution due to the α-FeCo and (FeCoNb)23B6 phases present after secondary crystallization.