Non-reciprocal voltage–current and impedance gyration effects in ferrite/piezoelectric toroidal magnetoelectric composites

A compact, efficient, and passive magnetoelectric (ME) gyrator consisting of a toroidal ferrite/piezoelectric composite and coil was developed, and its non-reciprocal V–I/I–V and bidirectional impedance conversion properties were systemically characterized. When a maximum V/I coefficient of 115 V/A over RL > 10 kΩ was obtained for the direct ME effect configuration, the output power reaches its maximum of 2.59 μW for optimum RL = 65 Ω at a constant input density of 48.4 μW/cm3, and when an inverse I/V coefficient was obtained, the output power reaches its maximum at 1.4 mA/V and 0.83 μW under optimum RL = 260 Ω and a constant input of 32.3 μW/cm3. Correspondingly, resistance-controlled capacitive/inductance tunabilities of 31 pF/Ω and 0.37 μH/Ω were achieved. Compared to traditional rectangular ME gyrators, the toroidal one has desired electromagnetic interference (EMI) tolerances due to its lower shape-induced anisotropy, near-zero demagnetization effects, and closed magnetic circuit. These findings provided more flexibility of the device design for efficient and compact power electronics deployed in circumstances where the lower EMI at higher frequencies was required.