Exchange Bias - Technological Impact

Technological Impact

Exchange bias was initially used to stabilize the magnetization of soft ferromagnetic layers in readback heads based on the anisotropic magnetoresistance (AMR) effect. Without the stabilization, the magnetic domain state of the head could be unpredictable, leading to reliability problems. Currently exchange bias is used to pin the harder reference layer in spin valve readback heads and MRAM memory circuits that utilize the giant magnetoresistance or magnetic tunneling effect. Similarly the most advanced disk media are antiferromagnetically coupled, making use of interfacial exchange to effectively increase the stability of small magnetic particles whose behavior would otherwise be superparamagnetic.

Desirable properties for an exchange bias material include a high Néel temperature, a large magnetocrystalline anisotropy and good chemical and structural compatibility with NiFe and Co, the most important ferromagnetic films. The most technologically significant exchange bias materials have been the rocksalt-structure antiferromagnetic oxides like NiO, CoO and their alloys and the rocksalt-structure intermetallics like FeMn, NiMn, IrMn and their alloys.