Magnetic effects at the interface between non-magnetic oxides

Brinkman, Alexander; Huijben, Mark; Zalk, Maarten van; Huijben, J.; Zeitler, U.; Maan, J.C.; Wiel, Wilfred G. van der; Rijnders, Guus; Blank, Dave H.A.; Hilgenkamp, H.

doi:10.1038/nmat1931

Cited by 1,666 publications

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“…However, remotely changing electronic states far from the adsorbed layer is possible, if these states are electrostatically coupled to the surface. Here we show that the surface adsorption of common solvents such as acetone, ethanol, and water can induce a large change in the conductivity at the buried interface between SrTiO 3 substrates and LaAlO 3 thin films [3][4][5][6][7][8] , and an adsorbate induced insulator to metal transition was observed when the thickness of LaAlO 3 , d LAO , is around 3 unit cells (uc). This phenomenon is observed only for polar solvents.…”

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confidence: 86%

Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

et al. 2011

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The interface between LaAlo 3 and srTio 3 possesses a range of intriguing properties, notably a proposed connection between the surface state of the LaAlo 3 and the conductivity buried in the srTio 3 . Here we study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlo 3 and srTio 3 . We show that the application of chemicals such as acetone, ethanol, and water can induce a large change in the conductivity, and, in particular, an insulator to metal transition around the critical LaAlo 3 thickness. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.

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confidence: 86%

Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

et al. 2011

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“…Examples include vortices in high temperature superconductors 1 , ferromagnetism at the interface between oxide band insulators 2 , and skyrmion phases in helimagnets 3,4 . Many experimental tools, including real space imaging techniques such as magnetic force microscopy (MFM) 5 , scanning superconducting quantum interference devices (SQUIDs) 6 and Lorentz transmission electron microscopy (TEM) 7 , and reciprocal space techniques including neutron scattering 8 have been successfully utilized to study magnetism in these systems.…”

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confidence: 99%

Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

et al. 2016

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High spatial resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogenvacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor based on its atomic size and quantum-limited sensing capabilities afforded by long spin coherence times. Although the NV center has been successfully implemented as a nanoscale scanning magnetic probe at room temperature, it has remained an outstanding challenge to extend this capability to cryogenic temperatures, where many solid-state systems exhibit non-trivial magnetic order. Here we present NV magnetic imaging down to 6 K with 6 nm spatial resolution and 3 μT/√Hz field sensitivity, first benchmarking the technique with a magnetic hard disk sample, then utilizing the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with Tc = 30 K. The expansion of NVbased magnetic imaging to cryogenic temperatures represents an important advance in state-of-theart magnetometry, which will enable future studies of heretofore inaccessible nanoscale magnetism in condensed matter systems. and Lorentz transmission electron microscopy (TEM) 7 , and reciprocal space techniques including neutron scattering 8 have been successfully utilized to study magnetism in these systems. However, each of these techniques has limitations that must be considered. In MFM, a ferromagnetic tip must be placed in close proximity to a sample, which can perturb the magnetic order that is being probed.Scanning SQUIDs typically require a probe temperature of 10 K or lower, and generally offer micron-size spatial resolution, although recent studies have enhanced the resolution to submicron scales 9 . Lorentz TEM can provide images with high spatial resolution and magnetic contrast, but requires very thin samples, typically less than 100 nm thick. Neutron scattering requires the growth of large, high purity single-crystal samples, and is an ensemble-averaged measurement. There is therefore a significant opportunity to develop a real-space, non-invasive magnetic sensor capable of studying magnetic order at sub-10 nm spatial resolution and sub-T/Hz DC field sensitivities.The nitrogen vacancy (NV) defect center in diamond is an exceptionally versatile single spin system with unique quantum properties that have driven its application in diverse areas ranging from quantum information and photonics to quantum metrology [10][11][12][13][14][15][16][17][18][19] . Cryogenic scanning magnetometry stands out as potentially the most impactful application of NV centers, taking advantage of the exquisite magnetic field sensitivity and intrinsic atomic scale of the NV center for high resolution imaging 20 . The operation of an NV-based magnetic probe is dependent on a fundamentally different sensing principle than other imaging methods, namely the spin-dependent photolum...

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“…LAO/STO is well known for showing interface conductivity between two otherwise insulating materials716181920212223. However, if the STO substrate is reduced during low oxygen pressure deposition a strong contribution of the bulk conduction of the STO is measurable67, while a deposition at high oxygen pressures can result in an undesirably high resistance1820. One of the central challenges of PLD processes is thus, the need of a low oxygen pressure to grow certain complex oxides and the accompanied undesired reduction of the thin film, the substrate or both.…”

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confidence: 99%

“…Numerous examples can be found in literature for the reduction of STO substrates during pulsed laser depositions for physical oxygen pressures below 10 −5 mbar6711161718202122. This opposes the results of chemically controlled reducing atmosphere annealing experiments (H 2 /Ar/O 2 mixtures), for which the sample is, in opposite to vacuum annealing, under a physical pressure of 1 bar.…”

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Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

Hensling

Gunkel

et al. 2017

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The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen.

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Magnetic effects at the interface between non-magnetic oxides

Abstract: The electronic reconstruction at the interface between two insulating oxides can

Cited by 1,666 publications

References 30 publications

Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

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