Abstract
An IrMn top-nailed spin-valve multilayer film was synthesized using direct-current magnetron sputtering on a naturally oxidized silicon substrate. The multilayered film microstructure and magnetism were analyzed using x-ray diffraction, transmission, and atomic force microscopies as well as vibrating sample magnetometry as functions of ion irradiation. The reverse saturation field residence time of the spin-valve multilayered sample was used to assess its magnetic stability. Ga+ distribution in the layers after irradiation was also simulated using the SRIM2003 package. Ga+ irradiation weakened the intensity of the (111) peak of the antiferromagnetic IrMn (111) layer, decreased surface roughness as well as exchange bias field and pinned layer coercive force, while increasing the free layer coercive force. However, the multilayer exchange bias field of the spin-valve film under the reverse saturation field after Ga+ irradiation did not change with time.
Highlights
A discovery of a giant magnetoresistance effect in Fe/Cr multilayered films by Baibich et al.1 in 1988 initiated enormous interest in this topic among scientists and engineers
The spin-valve multilayered film was irradiated using the FIB200XP instrument manufactured by Field Electron and Ion (FEI) at 30 keV ion acceleration voltage, 1000 pA beam current, 0○ injection angle, and 3 × 1014 ion cm−2 Ga+ dose
We studied the effect of the holding time of the reverse saturation field on the magnetization reversal process
Summary
A discovery of a giant magnetoresistance effect in Fe/Cr multilayered films by Baibich et al. in 1988 initiated enormous interest in this topic among scientists and engineers. In 1991, Dieny used an exchange coupling of the antiferromagnetic layers to design a spin-valve structure containing the following sequence of layers: (1) free ferromagnetic layer, (2) isolating non-magnetic layer, (3) ferromagnetic (pinned) layer, and (4) antiferromagnetic layer The advantages of this structure are low saturation field and high sensitivity, which can suppress Barkhausen noise. Yang et al. studied irradiation of the CoFe/PtMn bilayer membrane by carbon-ions and made an opposite conclusion that ion irradiation reduces the size of the exchange bias field To advance this field to industrial applications, an accurate understanding of the ion-irradiation effect on the microstructure, magnetic properties, and stability of the magnetic thin films is needed. In this paper, we studied the effect of Ga+ irradiation (performed using FIB) on the structure and magnetism of the multilayered CoFe/Cu/CoFe/IrMn spin-valve film using x-ray diffraction (XRD), transmission electron and atomic force microscopies (TEM and AFM, respectively), and vibrating sample magnetometry (VSM)
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