Field Sensors and Tunable Devices Using Magnetoelectric Hexaferrite on Silicon Substrates

Abstract

In this paper, the H-field and E-field sensors as well as the tunable devices are fabricated by utilizing single-phase magnetoelectric (ME) hexaferrite thin films on a silicon substrate. A buffer layer of indium–tin oxide is introduced between the Si wafer and the ME film. The required voltage excitations are reduced to values below 1 V at room temperature, hence making these devices compatible with planar integrated circuits (ICs) and CMOS. A planar spiral coil is utilized in a frequency range of 100 Hz to 10 MHz for sensing applications by applying an ac field (electric or magnetic) for excitation of the ME film. For H-field (E-field) sensing, a sensitivity of up to 1000 Vm $^{-1}$ /G ( $10^{-7}$ G/Vm $^{-1})$ is attained. The corresponding sensitivity for H-field is $4 \times 10^{4}$ up to $10^{7}$ V/T for 3 kHz up to 10 MHz. Tunability of up to 60% is achieved for tunable inductor applications; moreover, a change of 26% in voltage is observed at a single frequency by applying a voltage of 3 V on the ME film, thus performing as a single frequency detector. The proposed devices are made of single-phase materials, so they are simple to fabricate and capable to operate at the voltages of few volts; these features make them viable as a new generation of the ME devices for integration in ICs.