Converse magnetoelectric coupling in multilayer capacitors

Abstract

We report electrically induced changes of 20% in both the remnant magnetization and the coercive field of a magnetoelectric heterostructure. This heterostructure is an industrially produced multilayer capacitor comprising Ni-based magnetostrictive electrodes sandwiching a BaTiO3-based dielectric that is ferroelectric and therefore piezoelectric. Both magnetization and strain are shown to be hysteretic with applied electric field. These inexpensive capacitors might find use as electrically controlled ferromagnets.

Non-volatile electrically-driven repeatable magnetization reversal with no applied magnetic field

“…1b), and are larger than the 20-40 nm Ni grains measured by X-ray diffraction. The Ni electrodes in an unpolished MLC display shape anisotropy 31 with the hard-axis out-of-plane (Fig. 1c).…”

“…1c), evidence a small perpendicular magnetic stress anisotropy (Supplementary Note 1). An electric field that is large enough to produce strain-mediated changes of in-plane magnetization 31 had no discernible effect on out-of-plane magnetization M z ( Fig. 1c and Supplementary Fig.…”

“…Flattened MFM images (12 mm  7 mm) for a region of nominally exposed Ni in MLC#4 at (a) magnetic remanence after poling, and subsequently in zero electric field after having applied (b) þ200 V, (c) À200 V and (d) þ200 V across MLC terminals. The reversals in the sign of the applied voltage are likely not significant as they do not alter the high-field strain 31 . (e) Profiles along coloured lines in (a-d).…”

“…3) evidence a strong uniaxial z-axis anisotropy K ¼ À 3 2 l Ni s s (Supplementary Note 2), which arises due to isotropic in-plane stress s40 for Ni saturation magnetostriction l Ni s o0. This local tensile stress in the feature arises following the release 34 of global in-plane compressive stress, that is, after applying and subsequently removing a voltage 31 . The magnetic discontinuity between the feature and the surrounding film may have a structural origin, as the lateral feature size is consistent with the topographical features seen after etching (Fig.…”

“…3) is initiated when the voltage applied to the MLC terminals reduces K via a local reduction in s that is large enough to exceed the global in-plane compressive stress observed in macroscopic measurements of strain 31 …”