Fig. 4.

Magnetoelectric coupling via interfacial oxygen ion gating. a Schematic diagram of magnetic interactions in granular thin films. The hysteresis loops represent the extreme cases when intrinsic spin flipping $h_j^{\mathrm{s}}$ and inter-granular exchanges $h_j\left(m_i\right)$ dominate, respectively. b Schematic diagram of the magnetoelectric coupling via the segregated oxygen ionic accumulation-induced pinning effect and magnetic anisotropy at the interface, where the intrinsic magnetic flipping field $h_j^{\mathrm{s}}$ is enhanced for the high-resistance state (HRS). c Co thickness (t) dependence of the magnetoelectric coupling for Co/SrCoO_2.5 heterostructures. η is calculated by $\left(H_{\mathrm{C}}^{\mathrm{HRS}}-H_{\mathrm{C}}^{\mathrm{LRS}}\right)∕H_{\mathrm{C}}^{\mathrm{HRS}}$ as mentioned above, while the fitting function is defined as η = k/t. The inset shows the correlation between the coercive field modulation and the ON/OFF ratio of the resistance switch. The error bar is calculated from the standard deviation of results obtained in five different devices. d Magnetoelectric coupling with control of oxygen ion gating. The device is set to HRS at the beginning, and then different current limits are set to create the low-resistance state (LRS) with varied resistance values. For each LRS, the coercive field (H_C) was obtained through the measurement of the magnetic hysteresis. The star symbols represent the calculated H_C values from the ON/OFF ratio during the resistance switch. The error bars indicate the standard deviation from 10 measurements under an identical resistance state