Magnetic properties of epitaxial NiFe/Cu/Co spin-valve structures on GaAs(001)

Abstract

Cu(50 Å)/NiFe(60 Å)/Cu(60 Å)/Co(20 Å) epitaxial spin-valve structures were grown on GaAs(001) substrates by molecular-beam epitaxy at room temperature. In situ reflection high-energy electron diffraction measurements indicate the stabilization of the bcc-Co(001) phase on 1×1 unreconstructed GaAs(001) for thicknesses up to 20 Å and the epitaxial growth of the fcc-Cu(001) spacer layer and fcc-FeNi(001) top magnetic layer. Magneto-optical Kerr effect and Brillouin light-scattering measurements of the composite structure showed that a fourfold cubic anisotropy is present but a twofold anisotropy also occurs directed along the 〈110〉 axes. The easy cubic axes are directed along the 〈100〉 axes, which implies that the cubic anisotropy constant Kl for bcc-Co is positive. The magnetic anisotropy of the bcc-Co layer has a striking influence on the magnetoresistance characteristics which were found to be angular dependent. A simulation of this mixed anisotropy behavior yields quantitative agreement with the experimental results.

Mirror Domain Structures Induced by Interlayer Magnetic Wall Coupling

“…In situ reflection high-energy electron diffraction measurements show that the bottom Co magnetic layer has a bcc structure, whereas the Cu spacer layer and the top NiFe magnetic layer have fcc structures [9,10]. The large 60 Å Cu spacer layer thickness is chosen to minimize the effect of interlayer exchange coupling [11,12].…”

Magnetic Domain Confinement by Anisotropy Modulation

“…Continuous films of Cu(5 nm)͞Ni(5 nm)͞Cu(70 nm)͞Co(1.8 nm) were deposited onto the substrates in an ultrahigh vacuum system ͑10 210 mbar͒ using molecular beam epitaxy (MBE) techniques. The 1.8-nm-thick Co is used as a seed layer to promote epitaxial growth on the GaAs substrate [12]. A thickness of 5 nm is selected for the Ni layer in order to obtain a strong PMA [10] and the 5-nm-thick Cu overlayer is used to prevent oxidation.…”

Spin confinement by anisotropy modulation

“…Continuous films of Cu(5 nm)/Ni(5 nm)/Cu(70 nm)/Co(1.8 nm) were deposited onto the substrates in an ultrahigh vacuum system (10 −10 mbar) using molecular beam epitaxy (MBE) techniques. The 1.8 nm thick Co is used as a seed layer to promote epitaxial growth on the GaAs substrate [56]. A thickness of 5 nm is selected for the Ni layer in order to obtain a strong PMA [49,50,53] and the 5 nm thick Cu overlayer is used to prevent oxidation.…”