Magnetic-control-electric and reversal behavior of ZnO/NiFe/ZnO multilayer films

The magnetic-control-electric and corresponding dielectric behavior of the ZnO/NiFe/ZnO multilayer films have been demonstrated by applying an ultrathin bimetallic NiFe inserting layer into ZnO films, and fabricated by radio-frequency magnetron sputtering at room temperature without introducing any oxygen gas during deposition process. At first, a high quality crystalline ZnO(002) textured film was deposited and exhibited a dielectric constant value of around 10 confirmed at room temperature with the Agilent 42941B probe and 4294A impedance meters ranged from 40 Hz to 20 MHz. Once ZnO inserted with a 5 nm-thick NiFe inserting layer, the value of dielectric constant was dramatically increased from 10 to 12.5. This phenomenon can be attributed to redistribute the strongly interface charges between ZnO and NiFe layers and accompany with the relaxation of internal stress of ZnO. On the other hand, the external magnetic field induced dielectric variation can also be clearly observed, and the ZnO film with NiFe inserting layer demonstrates a 0.05%-0.10% dielectric tunability. The magnetic-control-electric and corresponding dielectric behavior of ZnO/NiFe/ZnO multilayers with a single inserting NiFe layer compared with that of pure ZnO film also conclude the magnetoelectric effect in present multilayered structures. Moreover, the grain size of the ZnO films was gradually increased from 32.5 nm to 40.5 nm while inserting with an ultrathin NiFe bimetallic layer. This grain structure transition can be attributed to the lattice misfit between ZnO and NiFe. This research work demonstrates that a single NiFe insering layer can effectively control the dielectric and magnetic characters in the ZnO/NiFe/ZnO multilayered structures and provide valuable multifunctional behaviors for potential novel applications design such as ferroic sensor.