Magnetic and Structural Properties of Exchange Coupled Heusler Alloy NiO/Co2FeAl Interfaces with n-and p-Type Silicon Substrates

Abstract

Exchange coupled structures of half metallic ferromagnets, Heusler Alloy (FM), Co2FeAl (CFA) and antiferromagnet (AF), NiO were fabricated by electron beam evaporation technique on n- and p-type Si substrates. These fabricated bilayer structures were further characterized for structural, morphological and magnetic point of views using x-ray diffraction (XRD), atomic/magnetic force microscopy (AFM/MFM) and vibrating sample magnetometer (VSM) techniques. Structural study shows the presence of CFA alloy and NiO phase. Surface morphology shows the granular feature of the top surface with grain size of 200–300 nm due to clustering of smaller grains. Smaller sized magnetic domains have been observed for the structures. Hysteresis behaviour of NiO/CFA/Si structures shows the ferromagnetic behaviour for in-plane orientation with negligible exchange bias whereas a significant exchange bias for out of plane orientation has been observed. The observed result could be understood due to surface roughness and arrangements of spins near the interface of ferromagnetic and anti-ferromagnetic layers.