Annealing Argon Electron scattering Ferromagnetism Giant magnetoresistance High temperature effects Interfaces (materials) Oxidation Secondary ion mass spectrometry Thermodynamic stability X ray photoelectron spectroscopy Ferromagnetic coupling Interlayer coupling fields Nano-oxide layers (NOL) Specular spin valves Nanostructured materials
Issue Date:
2004
Publisher:
Journal of Physics D: Applied Physics
Citation:
Volume 37, Issue 23, Page 3290-3295
Abstract:
Specular spin valves (SVs) containing nano-oxide layers (NOLs) structured as substrate/seed/AF/P
1/NOL/P2/Cu/F/NOL, have been fabricated. The NOLs were formed by natural oxidation in different
ambient atmospheres of pure oxygen, oxygen/nitrogen and oxygen/argon gas mixtures. The fabrication
conditions were optimized to enhance the magnetoresistance (MR) ratio, to suppress the interlayer coupling
fields (Hf) between the free and pinned layers, to suppress the high interface density of the NOL, to ease the
control of the NOL thickness and to form a smooth NOL/P2 interface for promoting specular electron
scattering. The characteristics of our specular SVs are the MR ratio of 14.1%, the exchange bias field of 44-
45 mT, and Hf weaker than 1.0 mT. The optimal conditions for oxidation time, total oxidation pressure and
the annealing temperature were found to be 300 s, 0.14 Pa (oxygen/argon = 80/20) and 250?C, respectively.
Also, the origin of thermal stability of MMn-based (M = Fe, Pt, Ir, etc) specular SVs has been explained in
detail by chemical properties of NOL using secondary-ion mass spectroscopy and x-ray photoelectron
spectroscopy depth profile analyses. Thermal stability turns out to be caused by a decrease in MR ratios at
high temperatures (>250?C), which is a serious problem for device applications using the SV structure as a
high density read head device.
