Perpendicular exchange bias and its control by magnetic, stress and electric fields

Perpendicular exchange bias (PEB) involving perpendicular magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the ferromagnetic (FM) sensor layer is expected to become important in future perpendicular recording and sensing devices. Further, because of the reduced spin dimensionality, PEB promises to be easier understandable than the conventional planar exchange bias (EB). In addition to its first realization using the Ising-type AF compounds FeF2 and FeCl2 we have tested control strategies of EB being alternative to the conventional magnetic and thermal ones. Indeed, specific symmetry properties of the pinning layer have been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric control (viz. magneto-electric via Cr2O3) of EB, respectively. Electric control promises to become relevant for TMR devices in MRAM technology. PACS. 75.50.Ee Antiferromagnetics – 75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures) – 75.70.Kw Domain structure (including magnetic bubbles) – 75.80.+q Magnetomechanical and magnetoelectric effects, magnetostriction