Magnetic hysteresis loop tuning in antiferromagnetically coupled bilayer structures

We have utilized antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. A key element of this approach is the nonoverlapping switching field distribution of the two magnetic layers. This allows measurement of the magnetization reversal in the soft-magnetic layer (SL) at low fields without perturbing the magnetic state of the hard-magnetic layer (HL). The magnetization of HL can be changed by an appropriate high-field sequence, which also modifies the effective disorder level in SL due to the antiferromagnetic interlayer coupling. Variations of the SL hysteresis loop squareness by a factor of up to 50 are reported by utilizing this fully reversible tuning procedure.