Voltage control of perpendicular magnetic anisotropy (PMA) is very promising in the realization of high-density, lightweight, and energy-efficient information storage. However, it is hard to achieve $E$-field regulation of PMA in conventional multiferroic laminates since the voltage-induced magnetic anisotropy is relatively small. In this study, we demonstrate $E$-field control of PMA in ${(\mathrm{Co}/\mathrm{Pt})}_3/\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_3\text{−}{\mathrm{PbTiO}}_3$ multiferroic heterostructures at room temperature using ferromagnetic resonance measurement (FMR) and a magnetic optical Kerr (MOKE) microscope. When a single Co layer $(t_{\mathrm{Co}})=1.0\mathrm{nm}$ PMA is obtained, a resonance shift up to 470 Oe is obtained with a $12\text{−}\mathrm{kV}{\mathrm{cm}}^{-1}$ $E$ field. Up to 75% perpendicular magnetic moments can be controlled with an applied $10\text{−}\mathrm{kV}{\mathrm{cm}}^{-1}$ electric field at $t_{\mathrm{Co}}=0.9\mathrm{nm}$ while little effect is obtained at $t_{\mathrm{Co}}=0.7\mathrm{nm}$. In addition, a multiferroic heterostructure with in-plane anisotropy is also studied at $t_{\mathrm{Co}}=1.4\mathrm{nm}$, and the resonance shifts are comparable to 1.0 nm. We relate this phenomenon to the instability of Co orbital moments near the critical transition area (0.9, 1.0, 1.4 nm). However, if $t_{\mathrm{Co}}$ is far from the transition point, the magnetic properties become insensitive to an external stimulus (0.7 nm). This voltage manipulation of PMA in ultrathin Co films should offer possibilities for realizing electronic devices and memories with great energy efficiency.

• Received 11 May 2017

DOI:https://doi.org/10.1103/PhysRevApplied.8.044006