Growth of single-crystal Fe/Cr magnetic multilayer structures on (001) GaAs by molecular beam epitaxy

Abstract

Molecular beam epitaxy (MBE) has been used to grow single-crystal Fe/Cr magnetic multilayer structures on (001) GaAs. The growth has been initiated on homoepitaxial GaAs layer in order to improve the smoothness of the substrate surface. Standard effusion cells were used for MBE growth of the GaAs homoepitaxial buffer layer, while specially designed high-temperature cells, heated by electron bombardment of a metallic crucible, were used in order to produce sufficiently high Fe and Cr fluxes. The epitaxial relationships between Fe, Cr and GaAs were determined by “in situ” reflection high-energy electron diffraction and verified “a posteriori” by X-ray diffraction. The sharpness of the different interfaces of the Fe/Cr multilayers is illustrated by Auger electron spectroscopy sputter depth profiles and scanning transmission electron microscopy, showing that no significant intermixing occurs in the investigated growth temperature range (– 50 to 50°C). Magnetic properties of multilayer structures with individual thicknesses of the Fe and Cr layers ranging between 9 and 60 Å are investigated. Magnetization measurements show that for Cr thickness below 30 Å antiferromagnetic ordering of the Fe layers occurs (i.e. the magnetization of neighbour Fe layers are antiparallel) due to interlayer coupling through the Cr layers. Giant magnetoresistance effects, which can exceed 40% of the total resistance of the sample, are also reported.