Giant magnetoelectric effect in perpendicularly magnetized Pt/Co/Ta ultrathin films on a ferroelectric substrate

Perpendicularly magnetized layers are essential for information storage to increase the storage density. Modulating perpendicular magnetization by an electric field offers a promising solution to lower energy consumption. Here, we demonstrate a remarkable electric field modulation of perpendicular magnetization in perpendicularly magnetized Pt/Co/Ta ultrathin films on a ferroelectric substrate. By measuring the anomalous Hall effect under in situ electric fields, we observe a giant magnetoelectric effect with the large converse magnetoelectric coefficient of -2.1 x 10(-6) s m(-1) at H-perpendicular to = -20 Oe and -0.9 x 10(-6) s m(-1) at H-perpendicular to = 0 Oe, which is comparable to that in multiferroic heterostructures with in-plane magnetization. Additionally, Kerr imaging shows that electric fields observably affect magnetic domain structures of the Pt/Co/Ta ultrathin films indicating a giant magnetoelectric effect. We further measure in situ X-ray diffraction and X-ray reflectivity with electric fields, which suggests that this giant magnetoelectric effect is attributed to strain-mediated magnetoelectric coupling and is closely related to electric-field-varied interface roughness. Our findings highlight the role of interface roughness in exploring electrical control of perpendicular magnetization.