Electronic voltage control of magnetic anisotropy at room temperature in high- κ SrTiO3/Co/Pt trilayer

Abstract

To improve power efficiency and endurance of magnetic memory technologies, a voltage-controlled mechanism is desirable. The voltage control of magnetic anisotropy (VCMA) effect in MgO stacks is a promising option, however, its strength is too low for memory applications. Replacing the standard MgO layer by an oxide with a higher permittivity $\ensuremath{\kappa}$ may help improve the VCMA strength. We demonstrate a VCMA effect up to $\ensuremath{\xi}=75$ fJ/Vm at room temperature in a Co\ensuremath{\setminus}Pt bilayer grown on atomic layer deposited (ALD) high-$\ensuremath{\kappa}\phantom{\rule{4pt}{0ex}}{\mathrm{SrTiO}}_{3}$ (STO). After treating the STO surface with isopropanol, a thin ${\mathrm{CoO}}_{x}$ interfacial layer is observed, enabling VCMA. Upon cooling down from room temperature to 200 K, the VCMA effect strength increases by a factor of two. This increase is incompatible with the expected Arrhenius temperature dependence for an ionic effect and thus we argue that the observed VCMA effect is electronic. Electronic VCMA is desirable for adequate memory endurance, and hence the approach proposed here has great potential for applications.