Magnetoresistance enhancement in specular, bottom-pinned, Mn83Ir17 spin valves with nano-oxide layers

Abstract

Bottom-pinned Mn83Ir17 spin valves with enhanced specular scattering were fabricated, showing magnetoresistance (MR) values up to 13.6%, lower sheet resistance R□ and higher ΔR□. Two nano-oxide layers (NOL) are grown on both sides of the CoFe/Cu/CoFe spin valve structure by natural oxidation or remote plasma oxidation of the starting CoFe layer. Maximum MR enhancement is obtained after just 1 min plasma oxidation. Rutherford backscattering analysis shows that a 15±2 Å oxide layer grows at the expense of the initial (prior to oxidation) CoFe layer, with ∼12% reduction of the initial 40 Å CoFe thickness. X-ray reflectometry indicates that Kiessig fringes become better defined after NOL growth, indicating smoother inner interfaces, in agreement with the observed decrease of the spin valve ferromagnetic Néel coupling.

Polarization‐Mediated Thermal Stability of Metal/Oxide Heterointerface

“…Below 300 °C, the magnitude of Co/IrMn(12 nm) exchange bias was stable. [ 40 ] According to previous reports, [ 41,42 ] the oxidation of the free layer reduces the effective magnetic thickness of the free layer, which depresses the spin-dependent bulk scattering effect and thus decreases the GMR effect. When the spin-dependent scattering is depressed, AP P R R − becomes smaller.…”

An Early Cancer Diagnosis Platform based on Micro-magnetic Sensor Array Demonstrates Ultra-high Sensitivity

“…This allows both magnetizations either parallel (low resistance) or antiparallel (high resistance) to be obtained with an externally applied magnetic field. The nano-oxide layer NOL inserted either adjacent to the pinned layer or free layers [46][47][48] can highly enhance the majority spin orientated electrons specularly scatter at NOL [49,50] and thus a high dR/R.…”

Characterization of nano-oxide layers fabricated by ion beam oxidation

“…using the Rutherford Backscattering Spectroscopy (RBS) technique, without any prior thermal treatment. For reference, one sample was prepared by natural oxidation: the bottom CoFe film was exposed to atmosphere for 15 min [4] in a class 100 clean room environment (30% controlled humidity, 20 C). The RBS experiments were carried out with a 1.6-MeV He beam (collimated 0.2 0.6 mm beam) in grazing angle incidence (77 tilt), and the backscattering angle was 160 in Cornell geometry.…”

“…Accurate values were obtained by X-rays, and the CoFe-oxide thickness was calibrated as 30 20% and 15 10% [4]. The nature of the oxide cannot be identified, but X-ray photon spectroscopy (XPS) indicated clearly the formation of Fe-oxide phases and not Co-oxide.…”