Magnetic vector field sensor using magnetoelectric thin film composites

In this paper, optimization of the response to a magnetic field H (ME_H effect) of magnetoelectric (ME) thin film composites and their usage for building a magnetic vector field sensor are examined. The ME composites described here consists of 0.68Pb(Mg_0.33Nb_0.67)O₃-0.32PbTiO₃ (PMN-PT) piezoelectric single crystals onto both sides of which a 4 μm thick multilayer of TbFe(7 nm)/FeCo(10 nm) is deposited. Measurements are carried out by applying magnetic DC and AC fields generated by a solenoid and Helmholtz coils, respectively. Results show that the magnetoelectric response is directly proportional to the magnetorestrictive susceptibility which is extremely field dependent. Maximum magnetostrictive susceptibility is achieved by annealing the samples to 275 °C and subsequently cooling them down in a magnetic field of 250 mT. This creates an in-plane magnetic anisotropy thereby increasing the ME effect along the hard axis after repolarization of the PMN-PT crystal. A discernible increase of the ME voltage as well as a clearly defined and small optimal bias field are observed. This optimization of the field response by domain design through magnetic field annealing allows the creation of magnetic vector field sensors.