Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO<sub>3</sub> Epitaxial Thin Film System

Niu, Wei; Liu, Wenqing; Gu, Min; Chen, Yongda; Zhang, Xiaoqian; Zhang, Minhao; Chen, Yequan; Wang, Ji; Du, Jun; Song, Fengqi; Pan, Xiaoqing; Pryds, Nini; Wang, Xuefeng; Wang, Peng; Xu, Yongbing; Chen, Yunzhong; Zhang, Rong

doi:10.1002/aelm.201800055

Cited by 34 publications

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“…Compared to previous reports of diluting the LAO layer with nonpolar STO, this new approach provides an opportunity to tune the carrier density of the interfacial 2DEL without changing the polar discontinuity across the interface (Figure S2a, Supporting Information). Moreover, thick LaMnO 3 films are often ferromagnetic when epitaxially grown on STO . Therefore, this approach can also be used to study the magnetic proximity effect at LAO/STO interfaces as reported in EuTiO 3 ‐buffered LAO/STO …”

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confidence: 99%

Diluted Oxide Interfaces with Tunable Ground States

et al. 2019

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as 2D superconductivity (SC), [4][5][6][7][8] magnetism, [9][10][11] and possible coexistence of these two, [12][13][14] providing an intriguing platform for multifunctional electronic devices.The carriers in the 2DEL of STObased heterostructures occupy the Ti 3d t 2g orbitals, where the in-plane d xy bands often have a lower energy than the out-ofplane oriented d xz /d yz due to the confinement of these orbitals at the interface. [1,15] Among the systems investigated so far, the epitaxial polar/nonpolar LAO/STO interface has drawn intensive attention and shows a typical carrier density, n s , of ≈4 × 10 13 cm −2 . [4] This high carrier density results in the population of orbitals with both d xy and d xz /d yz symmetry. The occupation of carriers in different subbands has previously been controlled reversibly using electrostatic gating, leading to a versatile tuning of the physical properties of the interface. [16] For example, by back gating the interface through the STO substrate, a Lifshitz transition was revealed at a critical carrier density of n c = 1.7 × 10 13 cm −2 , [6] above which the Fermi level starts to cross the bottom of the d xz /d yz bands. In proximity to n c , superconductivity exhibits a dome-shape as a function of gating voltage The metallic interface between two oxide insulators, such as LaAlO 3 /SrTiO 3 (LAO/STO), provides new opportunities for electronics and spintronics. However, due to the presence of multiple orbital populations, tailoring the interfacial properties such as the ground state and metal-insulator transitions remains challenging. Here, an unforeseen tunability of the phase diagram of LAO/STO is reported by alloying LAO with a ferromagnetic LaMnO 3 insulator without forming lattice disorder and at the same time without changing the polarity of the system. By increasing the Mn-doping level, x, of LaAl 1−x Mn x O 3 / STO (0 ≤ x ≤ 1), the interface undergoes a Lifshitz transition at x = 0.225 across a critical carrier density of n c = 2.8 × 10 13 cm −2 , where a peak T SC ≈255 mK of superconducting transition temperature is observed. Moreover, the LaAl 1−x Mn x O 3 turns ferromagnetic at x ≥ 0.25. Remarkably, at x = 0.3, where the metallic interface is populated by only d xy electrons and just before it becomes insulating, a same device with both signatures of superconductivity and clear anomalous Hall effect (7.6 × 10 12 cm −2 < n s ≤ 1.1 × 10 13 cm −2 ) is achieved reproducibly. This provides a unique and effective way to tailor oxide interfaces for designing on-demand electronic and spintronic devices. Oxide InterfacesThe surface of SrTiO 3 (STO) [1] or its interface to another oxide insulator such as the polar perovskite LaAlO 3 (LAO) [2] or the spinel γ-Al 2 O 3 [3] can host a 2D electron liquid (2DEL). In particular, the 2DEL at LAO/STO interface has been found to exhibit a wide spectrum of emergent phenomena such

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Diluted Oxide Interfaces with Tunable Ground States

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“…However, these spin‐polarized electrons have been detected often in the high carrier density range where both the d xy and d xz /d yz electrons are populated . Based on the ferromagnetism of LMO thin films on the STO, Gan et al later detected the anomalous Hall effect in oxide interfaces of LaAl 0.7 Mn 0.3 O 3 /STO where only the d xy band are populated …”

Section: Magnetic Fieldmentioning

confidence: 99%

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli

Christensen

Trier

Niu

et al. 2019

Adv Materials Inter

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Oxides are an exciting class of electronic materials which share key properties with conventional semiconductors, but also bring new intrinsic functionalities that are not used in most current electronics: superconductivity, ferro-, pyro-, and piezoelectricity, ferromagnetism, and multiferrocity. Among the large number of oxides, strontium titanate (SrTiO 3 , STO) has been the center of attention in numerous studies for more than half a century. STO both serves as a popular template for epitaxial growth of oxide thin films as well as by itself exhibiting an attractive palettes of properties, including Numerous of the greatest inventions in modern society, such as solar cells, display panels, and transistors, rely on a simple concept: An external stimulus is applied to a material and the response is then utilized. Oxides often exhibit a colorful palette of responses to external stimuli due to the close coupling between lattice, spin, orbital, and charge degrees of freedom. In particular, oxide heterostructures where oxide thin films are deposited on SrTiO 3 have proven to be a fertile playground for material scientists, and a vast amount of interesting theoretical and experimental studies showcase the wide tunabilities of these heterostructures when subjected to external stimuli. Here, the authors review how the properties of SrTiO 3 -based heterostructures can be changed by external stimuli using electric fields, magnetic fields, light, stress, particle bombardment, liquids, gases, and temperature. The application of a single stimulus or several stimuli combined often leads to unexpected changes in properties which can open up for designing new devices as well as expanding the boundaries of our understanding within fundamental science. Hall of Fame Article is a research scientist at the Technical University of Denmark, Department of Energy Conversion and Storage. He received his B.Sc. (2009) and M.Sc. (2012) in nanoscience from the University of Copenhagen, followed by his Ph.D. (2017) and postdoc (2018) from the Technical University of Denmark. His work is currently focused on the physics of oxide materials and oxide devices for information technology and energy harvesting, including oxide electronics, memristors, internet of things, and thermoelectricity. Felix Trier is a postdoctoral researcher at CNRS/Thales, University Paris-Saclay. He obtained his B.Sc. (2009) and M.Sc. (2012) in nanoscience from the University of Copenhagen. Then he earned his Ph.D. degree (2016) from the Technical University of Denmark. His current research is focused on fabrication and characterization of metallic oxide heterointerface devices for the study of the spin-charge interconversion in 2D Rashba systems. His work concerns the LaAlO 3 /SrTiO 3 heterointerface 2D metal and its electrostatic tunability.Nini Pryds is a Professor and head of the research section "Functional Oxides" at the Department of Energy Conversion and Storage, Technical University of Denmark (DTU), where he is leading a group of researchers working in the field...

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“…One example for the second case is the LaMnO 3 /SrTiO 3 interface, of which the real spatial distribution of the magnetization is imaged as shown in Figure e . At this LaMnO 3 /SrTiO 3 interface, critical thickness modulation and multivalence Mn ions have also been investigated. After the charge transfer, the coexistence of Mn 2+ and Mn 3+ is observed at the interface with no indication of Mn 4+ at the surface .…”

Section: Emergent Phenomena At Functional Oxide Interfacesmentioning

confidence: 99%

Interface Engineering and Emergent Phenomena in Oxide Heterostructures

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Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital, and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking, and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems but also provide potentials for exploring next-generation electronic devices with high functionality. Herein, some recently developed strategies in engineering functional oxide interfaces and their emergent properties are reviewed.

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Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO₃ Epitaxial Thin Film System

Cited by 34 publications

References 59 publications

Diluted Oxide Interfaces with Tunable Ground States

Diluted Oxide Interfaces with Tunable Ground States

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli

Interface Engineering and Emergent Phenomena in Oxide Heterostructures

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Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO3 Epitaxial Thin Film System

Cited by 34 publications

References 59 publications

Diluted Oxide Interfaces with Tunable Ground States

Diluted Oxide Interfaces with Tunable Ground States

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO3‐Based Heterointerfaces with External Stimuli

Interface Engineering and Emergent Phenomena in Oxide Heterostructures

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Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO₃ Epitaxial Thin Film System

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO₃‐Based Heterointerfaces with External Stimuli