Abstract

The effects of antiferromagnetic corrosion on the magnetic properties of exchange biased thin films were studied. A Ni81Fe19/Ir20Mn80 bilayer was grown using DC sputtering. The crystal structure, microstructure, and magnetic properties of the samples were examined using x-ray diffraction (XRD), scanning electron microscope along with energy dispersive spectrometer, and resonance-vibrating sample magnetometer, respectively. XRD patterns revealed that the crystalline structure was (111) for both IrMn and NiFe layers. After magnetic field cooling, the room-temperature exchange bias field and coercive field were determined from hysteresis loops and no training effect was observed during the remagnetization process. The magnetic properties of the exchange biased bilayer strongly depended on the level of Mn corrosion in deionized (DI) water. A step-like magnetization curve was observed in the bilayer after soaking in DI water for 10 min. A detailed analysis of the magnetic moment response indicated an increase in the depth and area of corroded Mn with increasing soaking time. Trace amounts of Mn2+ in DI water, detected by a spectrophotometric technique using 1-(2-pyridylazo)-2-naphthol as an indicator, confirmed increasing Mn corrosion with increasing soaking time.

Highlights

  • Exchange bias (EB) is a phenomenon associated with the exchange interaction created at the interface of a ferromagnetic (FM) and an antiferromagnetic (AFM) material

  • Discovered by Meiklejohn and Bean in 19561 when studying ferromagnetic Co particles embedded in antiferromagnetic CoO, the effect has attracted much attention for pinning the magnetization of an FM layer in spin valves and magnetic tunnel junctions, a phenomenon used to measure magnetic fields,2–4 especially in hard disk drives

  • In order to eliminate the difference in magnetic moment due to sample mounting and replacement, the resonance-vibrating sample magnetometer (R-VSM) was designed and developed for the investigation of the magnetic properties of the exchange biased thin film in this work

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Summary

INTRODUCTION

Exchange bias (EB) is a phenomenon associated with the exchange interaction created at the interface of a ferromagnetic (FM) and an antiferromagnetic (AFM) material. Discovered by Meiklejohn and Bean in 19561 when studying ferromagnetic Co particles embedded in antiferromagnetic CoO, the effect has attracted much attention for pinning the magnetization of an FM layer in spin valves and magnetic tunnel junctions, a phenomenon used to measure magnetic fields, especially in hard disk drives. The effects of Mn corrosion on the magnetic properties of Ni81Fe19/Ir20Mn80 exchange biased bilayers were investigated. The Mn content in the antiferromagnetic IrMn layer decreases with increasing soaking time and varies from point-to-point on the AFM layer. This causes a step-like magnetization response to the applied magnetic field of the corroded NiFe/IrMn exchange biased system, which can affect the accuracy of magnetic field sensing

Sample preparation
Sample characterization
Corrosion investigation
RESULTS AND DISCUSSION
CONCLUSIONS

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