Gate-tuned anomalous Hall effect driven by Rashba splitting in intermixed LaAlO3/GdTiO3/SrTiO3

Abstract

The Anomalous Hall Effect (AHE) is an important quantity in determining the properties and understanding the behaviour of the two-dimensional electron system forming at the interface of SrTiO3-based oxide heterostructures. The occurrence of AHE is often interpreted as a signature of ferromagnetism, but it is becoming more and more clear that also paramagnets may contribute to AHE. We studied the influence of magnetic ions by measuring intermixed LaAlO3/GdTiO3/SrTiO3 at temperatures below 10 K. We find that, as function of gate voltage, the system undergoes a Lifshitz transition while at the same time an onset of AHE is observed. However, we do not observe clear signs of ferromagnetism. We argue the AHE to be due to the change in Rashba spin-orbit coupling at the Lifshitz transition and conclude that also paramagnetic moments which are easily polarizable at low temperatures and high magnetic fields lead to the presence of AHE, which needs to be taken into account when extracting carrier densities and mobilities.

Tunable Magnetic Scattering and Ferroelectric Switching at the LaAlO$_3$/EuTiO$_3$/Sr$_{0.99}$Ca$_{0.01}$TiO$_3$ Interface

“…Recently, LAO/STO interfaces were fabricated with GdTiO 3 interlayers instead of EuTiO 3 26 . These interfaces present similar, gate-tunable non-linear Hall signatures to those observed in the LAO/ETO/STO interface.…”

On the resistance minimum in LaAlO$_3$/Eu$_{1-x}$La$_x$TiO$_3$/SrTiO$_3$ heterostructures

“…Furthermore, below 10 K, there is also a low-field non-linearity in the magnetically doped samples. This indicates the presence of an Anomalous Hall Effect (AHE), which has often been observed and analysed 2,3,8,10 in order to determine the carrier concentrations n i and mobilities µ i of both bands, and the Anomalous Hall coefficient R AHE . Our analysis uses a substraction method described earlier in Ref.…”

“…Our analysis uses a substraction method described earlier in Ref. 8 . Details are included in the Supplementary, where we also introduce an effective magnetic moment M ef f to take account of the presence of the AHE.…”

“…One outstanding feature, of interest for spintronics applications, is the tunability of the spin polarisation or magnetism. Its signature, the Anomalous Hall effect (AHE), was extensively studied in the past decade in various STO-based structures [1][2][3][4][5][6][7][8][9] . It was shown, in particular, that the AHE can be completely switched off by a gate voltage, at least in some of this structures.…”

Observation of the Anomalous Hall Effect in NdTiO3/SrTiO3 Heterostructures

“…The AHE in this system is believed to arise from the skew scattering. , Due to the close theoretical resemblance between the AHE and the spin Hall effect, there are also ongoing efforts in realizing a robust AHE at elevated temperatures. Several such attempts have been made by introducing a magnetic element in either the STO substrate or in the LAO layer or by introducing an additional magnetic buffer layer. − …”