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Electron spin diffusion at the interface of multiferroic oxides

We study the spin diffusion in a two-dimensional electron gas at the interface of oxide heterostructure LaAlO$_3$/SrTiO$_3$ grown on multiferroic TbMnO$_3$ at 15 K by means of the kinetic spin Bloch equation approach. The spiral magnetic moments of Mn$^{3+}$ in TbMnO$_3$ interact with the diffusing spins at the LaAlO$_3$/SrTiO$_3$ interface via the Heisenberg exchange interaction. It is demonstrated that the spin diffusion length is always finite, despite the polarization direction of the injected spins. Our study also reveals the important role played by the Coulomb scattering, which can effectively suppress the spin diffusion.