Weak magnetic moment on IrMn exchange bias pinning layers

Abstract

We present evidence from soft x-ray resonant magnetic scattering measurements at the Mn L3 edge for the existence of a small magnetic moment on the antiferromagnetic IrMn pinning layer in a NiFe/Cu/Co/IrMn spin valve structure. The variation of the signal in an applied magnetic field shows that the moment lies antiparallel to the Co moment. Changes in the Mn L3 edge signal as the Co moment is rotated into the hard direction are rapid and do not appear to be associated with thermal reordering of the antiferromagnetic domain structure.

Multiple antiferromagnet/ferromagnet interfaces as a probe of grain-size-dependent exchange bias in polycrystalline Co/Fe50Mn50

“…The latter model has proven to be particularly useful and can be used to qualitatively explain the behavior of many systems [e.g. [25][26][27]. As an example, it has been shown that deliberately reducing the grain size in polycrystalline systems, hence increasing the density of grain boundaries and therefore uncompensated spins, can enhance H E [28].…”

Influence of the annealing field strength on exchange bias and magnetoresistance of spin valves with IrMn

“…The exchange bias effect in these systems depends on the uncompensated interfacial spin structure in the IrMn layer. 18,19 Spin reversal in the antiferromagnetic layer is thermally activated and therefore it depends critically on the experimental conditions ͑temperature and field sweep rate͒ and the energy barrier distribution. At room temperature and at low-field sweep rates only some of the uncompensated spins are pinned, i.e., they do not rotate in an external magnetic field.…”

Correlation between Exchange Bias and Pinned Interfacial Spins

“…Uncompensated spins associated with antiferromagnets or their interfaces have been observed in several systems, such as CoO/MgO [6] using SQUID or Co/FeMn [7], Co/IrMn [8] and Co/NiO [9] using XMCD. In particular, the study of Co/NiO showed that the existence of uncompensated interfacial spins is insufficient for exchange bias since they may more strongly couple to and rotate with the ferromagnet, yielding no bias.…”