Electric field tunability of microwave soft magnetic properties of Co₂FeAl Heusler alloy film

Co₂FeAl Heusler alloy film with 100 nm in thickness was sputtered on (011)-cut lead zinc niobate-lead titanate (PZN-PT) single crystal slabs. It was revealed that this multiferroic laminate shows very large electric field (E-field) tunability of microwave soft magnetic properties. With the increase of electric field from 0 to 8 kV/cm on PZN-PT, the anisotropy field, H_K, of the Co₂FeAl film along [100] direction of PZN-PT is dramatically enhanced from 65 to 570 Oe due to the strong magnetoelectric (ME) coupling between ferromagnetic Co₂FeAl film and ferroelectric substrate. At the same time, the damping constant α of Co₂FeAl film dramatically decreases from 0.20 to 0.029. As a result, a significantly shift of self-biased ferromagnetic resonance frequency, f_FMR, from 1.86 to 6.68 GHz with increment of 3.6 times was obtained. These features demonstrate that Co₂FeAl/PZN-PT multiferroic laminate is promising in fabrication of E-field tunable microwave components.