Prediction of two-dimensional electron gas mediated magnetoelectric coupling at ferroelectric PbTiO3/SrTiO3 heterostructures

First-principles calculations predict the emergence of magnetoelectric coupling mediated by two-dimensional electron gas (2DEG) at the ferroelectric ${\mathrm{PbTiO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructure. Free electrons endowed by naturally existing oxygen vacancies in ${\mathrm{SrTiO}}_{3}$ are driven to the heterostructure interface under the polarizing field of ferroelectric ${\mathrm{PbTiO}}_{3}$ to form a 2DEG. The electrons are captured by interfacial Ti atoms, which surprisingly exhibits ferromagnetism even at room temperature with a small critical density of $\ensuremath{\sim}15.5\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}^{2}$. The ferroelectricity-controlled ferromagnetism mediated by interfacial 2DEG shows strong magnetoelectric coupling strength, enabling convenient control of magnetism by electric field and vice versa. The ${\mathrm{PbTiO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructure is cheap, easily grown, and controllable, promising future applications in low-cost spintronics and information storage at ambient condition.