Large Converse Magnetoelectric Properties Without Bias in Composite of Rosen-Type Piezoelectric Transformer and Magnetization-Graded Ferromagnetic Material

We designed a magnetoelectric (ME) composite by bonding the graded-magnetostrictive layers of FeCuNbSiB/FeNi-ferromagnetic constant elasticity (FACE) on the output section of the Rosen-type transformer, in which a much higher self-biased converse magnetoelectric (CME) coefficient is obtained. Due to the different magnetic characteristics of nanocrystalline foil FeCuNbSiB and FeNi-FACE (such as magnetic permeability and coercivity), the FeCuNbSiB/FeNi-FACE layer exhibits an internal magnetic bias field. When the ac voltage is applied on the input section of the transformer, a large strain is mechanically transferred to the graded-magnetostrictive layers due to the stress concentration effect at full-wavelength resonance frequency. Therefore, the large strain in the output section of the Rosen-type transformer associated with the internal magnetic bias field in FeCuNbSiB/FeNi-FACE leads to a large self-biased CME coefficient. The experimental results demonstrate that: 1) a large remnant CME coefficient of 0.02058 mG/V is achieved, which is ~17 times higher than the previous results; 2) two stable magnetic flux states are generated by switching a smaller electric field of 10 V/cm ON/OFF alternately without magnetic bias field, which can be used as miniature electric-field-written high-density ME memory devices with lower energy consumption; and 3) the composite shows an approximately linear relationship between applied ac voltage Vin and induced magnetic induction B.