Surface oxidation of Permalloy thin films

Abstract

The chemical and magnetic structures of oxides on the surface of Permalloy Ni 81 Fe 19 films were investigated as functions of annealing time with x-ray and polarized neutron reflectometry. For annealing times of less than one hour, the oxide consisted of a 1.5-nm-thick layer of NiO on an Fe oxide layer that was in contact with Permalloy. The Fe oxide thickness increases with annealing time with a parabolic rate constant of 10 −18 cm 2 s −1 ͑for an annealing temperature of 373 K͒. The growth of the oxide layer is limited by the rate at which oxygen appears below the NiO layer. No portion of the oxide region was found to be ferromagnetically ordered for films annealed less than one hour. The growth of the Fe oxide region is well correlated with the measured increase of the second-order magnetic susceptibility for similarly prepared samples.

Magnetization reversal of an individual exchange-biased permalloy nanotube

“…The Py NT's data are compatible with a superposition of spectra of NiO and metallic Ni, which suggests the presence of a layer of NiO, in agreement with previous studies [34,35]. These results point to a layered composition of oxidized Py in the following sequence: Py/(α-Fe 2 O 3 or FeO)/NiO [35]. All three oxides are antiferromagnetically ordered below a certain ordering temperature (FeO: 198 K, α-Fe 2 O 3 : 95 K, NiO: 525 K) in the bulk [36].…”

Thermal spin injection and interface insensitivity in permalloy/aluminum metallic nonlocal spin valves

“…The most likely cause for the reduced electrical spin injection is the formation of oxidized permalloy at the FM/NM junction that was not fully removed by the RF cleaning step before Al deposition. Native permalloy oxides can be complicated chemically and magnetically [62], though typically are not seen to develop long-range magnetic order above ∼ 30 K [63][64][65]. However, the permalloy oxide is a likely source of intermediate energy states in the barrier with random local magnetic environments that could easily contribute to loss of spin fidelity as initially spin-polarized electrons transport from Py to Al.…”

Magnetoresistance Effect in NiFe/BP/NiFe Vertical Spin Valve Devices

“…A possible reason for this reduced polarization is the exposure to air of the Py surface prior to the application of the BP layer. Some contaminants are inevitably adsorbed on the surface and air exposure of Py may produce antiferromagnetic NiO, significantly decreasing the spin polarization [22]. Future well-controlled fabrication process in situ without air exposure of the interfaces may improve the interface quality, maximizing the MR effect.…”