Critical thickness for ferromagnetism in LaAlO3/SrTiO3 heterostructures

Kalisky, Beena; Bert, Julie A.; Klopfer, Brannon B.; Bell, C. H.; Sato, Hiroki; Hosoda, Masayuki; Hikita, Y.; Hwang, Harold Y.; Moler, Kathryn A.

doi:10.1038/ncomms1931

Cited by 207 publications

(228 citation statements)

References 30 publications

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“…While magnetic patches were detected using scanning SQUID microscopy with a very small average moment per interface unit cell area of 0.02 Bohr magneton, torque measurements revealed a large response with an average moment per interface unit cell area of 0.3 Bohr magneton. Furthermore, experiments performed at Stanford [65] did not seem to reveal any particular sensitivity of the magnetic response to the external electric field. These results raise a number of issues that are currently under intense scrutiny.…”

Section: Bulk and Interface Superconductivitymentioning

confidence: 91%

Interface superconductivity

Gariglio

Gabay

Mannhart

et al. 2015

Physica C: Superconductivity and its Applications

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Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO 3 and SrTiO 3 .We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO 3 and the interface system and the possible role of the interfacially induced Rashba type spin-orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T c in a monolayer of FeSe deposited on SrTiO 3 .

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Section: Bulk and Interface Superconductivitymentioning

confidence: 91%

Interface superconductivity

Gariglio

Gabay

Mannhart

et al. 2015

Physica C: Superconductivity and its Applications

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“…The LaAlO 3 /SrTiO 3 interface is a paradigm example, exhibiting conducting two-dimensional (2D) electron gas (2DEG) 3,4 and magnetism [5][6][7][8][9][10][11] between two insulating nonmagnetic metal oxides. In the [001] direction, two different interfaces can be formed between polar LaAlO 3 , which consists of alternating LaO) þ -(AlO 2 ) À layers, and nonpolar SrTiO 3 , which consists of alternating (SrO) 0 -(TiO 2 ) 0 layers.…”

mentioning

confidence: 99%

“…One is LaO/TiO 2 stacking configuration (so-called n-type) and the other is AlO 2 / SrO configuration (so-called p-type). The remarkable feature is that the conductivity occurs only at n-type interfaces when the LaAlO 3 film thickness (n LAO ) is larger than three unit cells (uc) 4,5 , whereas the magnetism has been observed both at n-type interfaces with n LAO 4B3 uc and at insulating p-type interfaces 8 . Table 1 lists some experimental observations representing the main puzzles 12 that need to be resolved before the promised applications can be realized 13 .…”

mentioning

confidence: 99%

A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces

2014

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The discovery of conductivity and magnetism at the polar-nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO 3 and SrTiO 3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO 3 / SrTiO 3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar-nonpolar interfaces.

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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. However, each of these techniques has limitations that must be considered.…”

mentioning

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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Critical thickness for ferromagnetism in LaAlO3/SrTiO3 heterostructures

Cited by 207 publications

References 30 publications

Interface superconductivity

Interface superconductivity

A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces

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

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