Abstract
The development of novel nano-oxide spintronic devices would benefit greatly from interfacing with emergent phenomena at oxide interfaces. In this paper, we integrate highly spin-split ferromagnetic semiconductor EuO onto perovskite SrTiO3 (001). A careful deposition of Eu metal by molecular beam epitaxy results in EuO growth via oxygen out-diffusion from SrTiO3. This in turn leaves behind a highly conductive interfacial layer through generation of oxygen vacancies. Below the Curie temperature of 70 K of EuO, this spin-polarized two-dimensional t2g electron gas at the EuO/SrTiO3 interface displays very large positive linear magnetoresistance (MR). Soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) reveals the t2g nature of the carriers. First principles calculations strongly suggest that Zeeman splitting, caused by proximity magnetism and oxygen vacancies in SrTiO3, is responsible for the MR. This system offers an as-yet-unexplored route to pursue proximity-induced effects in the oxide two-dimensional t2g electron gas.
Highlights
The high mobility two-dimensional t2g electron gas (2DEG) present at oxide/oxide interfaces is currently under intense investigation[1]
The crystalline EuO thin films are ferromagnetic below the Curie temperature of 70 K with a saturation moment ~6.3 μB/Eu.as demonstrated by superconducting quantum interference device (SQUID) magnetometer
Density functional theory (DFT) analysis based on the x-ray diffraction (XRD)/scanning transmission electron microscopy (STEM)-derived structural model provides a consistent picture of the band alignment, magnetic state of EuO, and electronic structure of the oxygen-deficient conductive layer formed in STO
Summary
The high mobility two-dimensional t2g electron gas (2DEG) present at oxide/oxide interfaces is currently under intense investigation[1]. Among the various mechanisms for the oxide 2DEG formation, one viable approach involves tailoring an interface between SrTiO3 (STO) and oxides with large negative enthalpy of formation such as EuO21 to stabilize a confined conducting layer of SrTiO3−δ22,23. Low-temperature transport measurements were performed in the physical property measurement system (PPMS) These EuO/STO heterostructures display temperature-dependent linear positive magnetoresistance below the Curie temperature. First principles calculations show that magnetoresistance is proportional to spin polarization that is linear in field due to the Zeeman effect Combining these results, we uncover the role of the spin-polarized oxygen vacancy as the origin of the linear positive magnetoresistance stemming from the ferromagnetism of Eu2+ magnetic moments in proximity to the confined oxygen-deficient conductive layer
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