Reversible hysteresis loop tuning

We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching fi eld distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The nonoverlapping switching fi eld distribution allows the measurement of magnetization reversal in the SL at low fi elds while keeping the magnetization state of the HL unperturbed. Applying an appropriate high fi eld or high fi eld sequence changes the magnetic state of the HL, which then infl uences the SL magnetization reversal due to the interlayer coupling. In this way, the position and shape of the SL hysteresis loop can be changed or tuned in a fully reversible and highly effective manner. Here, we study specifi cally how the SL hysteresis loop characteristics change as we move the HL through an entire high fi eld hysteresis loop sequence.