Metastable Phase Formation by Ion Beam Mixing for the Al–Mn System

Abstract

The metastable τ phase of Al–Mn with ferromagnetism is formed directly by ion beam induced mixing with 400 keV Xe+, 290 keV Kr+ and 150 keV Ar+ ions. The magnetic properties strongly depend on the ion dose, ion species, thickness ratio of Al to Mn layer and substrate temperature during ion irradiation. The maximum value of the saturation magnetization σ achieved is 36 emu / g, which corresponds to about 40 at% of the alloyed layer estimated from the bulk σ value. The grain size of the metastable τ phase is observed to be 10–40 nm by transmission electron microscopy (TEM). The present work has clarified the kinetics of ion beam mixing and the growth mechanism of the metastable phase. It is concluded that collision cascades connected dynamically with the radiation-enhanced diffusion play a decisive role in forming directly the metastable τ phase.