Electric Field Control of Spin Lifetimes inNb−SrTiO3by Spin-Orbit Fields

Abstract

We show electric field control of the spin accumulation at the interface of the oxide semiconductor Nb-SrTiO_{3} with Co/AlO_{x} spin injection contacts at room temperature. The in-plane spin lifetime τ_{∥}, as well as the ratio of the out-of-plane to in-plane spin lifetime τ_{⊥}/τ_{∥}, is manipulated by the built-in electric field at the semiconductor surface, without any additional gate contact. The origin of this manipulation is attributed to Rashba spin orbit fields (SOFs) at the Nb-SrTiO_{3} surface and shown to be consistent with theoretical model calculations based on SOF spin flip scattering. Additionally, the junction can be set in a high or low resistance state, leading to a nonvolatile control of τ_{⊥}/τ_{∥}, consistent with the manipulation of the Rashba SOF strength. Such room temperature electric field control over the spin state is essential for developing energy-efficient spintronic devices and shows promise for complex oxide based (spin) electronics.

Physics of SrTiO3-based heterostructures and nanostructures: a review

“…Many of the experiments performed so far were inspired by experiments first performed with semiconductors like silicon and GaAs. [499][500][501][502][503][504][505]; spin-charge conversion by spin pumping followed inverse Edelstein effect (IEE) [478,506].…”

Origin of the Magnetoresistance in Oxide Tunnel Junctions Determined through Electric Polarization Control of the Interface

“…Combining such dramatic effects with SrTiO 3 , a semiconductor with high mobilities [16,17] and potentially long spin lifetimes [18], could lead to novel spintronic devices. To date, the primary experimental evidence for spin injection into SrTiO 3 is through the 3T approach, interpreted in terms of spin accumulation in ILS [3,4] (or the SrTiO 3 itself [19]), similar to Si and GaAs [2,5,13]. The epitaxial LaAlO 3 =SrTiO 3 ð001Þ heterostructure is one system with tunable interface properties, arising from the stacking of AlO − 2 and LaO þ charged layers.…”

Evolution of the magnetoresistance lineshape with temperature and electric field across Nb-doped SrTiO3 interface

“…STO single crystals exhibit a large dielectric permittivity ( r ) at room temperature, that is anisotropic in different crystalline directions and increases non-linearly with temperature, electric field and frequency [20][21][22] . Doping of Nb, La at the Ti site transforms it into a degenerate ionic semiconductor (n-doped) with unconventional charge transport characteristics, triggered by the strong temperature and electric field dependence of the intrinsic dielectric permittivity 22,23 .Additionally, the broken inversion symmetry at the surface of STO leads to Rashba spin-orbit fields 24,25 which when tuned by electric fields either at the interface of a 2-DEG (LAO-STO) or at the interface of Nb-doped SrTiO 3 (Nb:STO) with Co/AlO x results in tuning of spin transport parameters as demonstrated in recent works 4,5 .…”

“…Keywords: Complex Oxides, Spin injection, electric field, Tunneling Anisotropic Magnetoresistance (TAMR) Spin voltage measured at different semiconducting interfaces have been widely studied using different combination of materials as spin contacts and employing different measurement techniques. Such studies are commonly performed using the popular three terminal (3T) and four terminal non-local (NL) geometries [1][2][3][4][5][6] . In spite of the fact that both these electrical transport schemes fail to resolve outstanding issues related to the precise understanding, origin and magnitude of spin accumulation across semiconducting interfaces, these are more accentuated using the 3T geometry [7][8][9][10][11] .…”