Strain-sensitive spin-state ordering in thin films of perovskite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext>LaCoO</mml:mtext><mml:mn>3</mml:mn></mml:msub></mml:math>

Fujioka, Jun; Yamasaki, Y.; Doi, A.; Nakao, Hironori; Kumai, Reiji; Murakami, Youichi; Nakamura, Masao; Kawasaki, Masashi; Arima, T.; Tokura, Y.

doi:10.1103/physrevb.92.195115

Cited by 34 publications

(39 citation statements)

References 36 publications

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“…It is worth mentioning that this Ferri phase may correspond to the ferrimagnetic phase observed recently in the epitaxial LaCoO 3 sample. 25) The present results suggest a possibility of the EIM phase in the low temperature side of the ferrimagnetic phase.…”

Section: Iησsupporting

confidence: 55%

Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom — Implications for an Excitonic Insulator —

et al. 2016

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Magnetic field (H) effects on a correlated electron system with the spin-state degree of freedom are examined. The effective Hamiltonian derived from the two-orbital Hubbard model is analyzed by the mean-field approximation. Applying H to the low-spin (LS) phase induces the excitonic insulating phase, as well as the spin-state ordered phase where the LS and high-spin (HS) states are ordered alternately. In the case where H is applied to the HS phase, a reentrant transition for the HS phase appears. A rich variety of the phase diagrams are attributed to the spin-state degree of freedom and their combinations in the wave function as well as in the real-space configuration. Present results provide a possible interpretation for the recent experimental observation under the strong magnetic field in LaCoO 3 . KEYWORDS: spin state, magnetic field, excitonic insulatorSpin-state degree of freedom (SSDF) in the transitionmetal ions have been widely recognized as one of the indispensable factors which provide rich variety of physics in magnetic solids. There are multiple spin states in a single magnetic ion due to the different local electron configurations. Transitions between the multiple spin states are often seen in the iron and cobalt ions which are included not only in correlated electron materials, 1-3) but also in biomaterials, 4) and earth innercore materials. 5-7) A driving force of the spin-state transition is attributed to a competition between the crystalline-field effect and the Hund's coupling, which stabilize the low-spin (LS) and high-spin (HS) states, respectively. 8,9) Perovskite cobalt oxides and their derivatives are the prototypical examples of the correlated electron materials with SSDF. A nominal valence of the cobalt ion in LaCoO 3 is 3+ where the number of electrons occupying the 3d orbitals is six. The characteristic temperature dependences of the electrical resistivity and the magnetic susceptibility are interpreted as a crossover between the LS state of the (t 2g ) 6 configuration with S = 0 and the HS states of (t 2g ) 4 (e g ) 2 with S = 2. 2) Several exotic phenomena, such as the giant magnetoresistance, 10) magnetic clusters, 11,12) and a ferroelectricity, 14) are attributable to the spin-state change.Correlated electron materials with SSDF is recently reexamined as a plausible candidate of the excitonic insulator (EI). [15][16][17] The EI state has been studied since 1960s in the narrow gap semiconductors and semimetals, [18][19][20][21][22] and is recently reexamined from the modern viewpoints. 23,24) The EI state is expected to be realized, when the exciton binding energy exceeds the band gap energy. Since the LS and HS states in the cobalt oxides are identified as a band insulator and a Mott insulator, respectively, a narrow-gapped state is expected around a crossover between the two spin states. Actually, a phase transition around 90K observed in Pr 0.5 Ca 0.5 CoO 3 is examined from the viewpoints of the EI phase transition. 16) It is required to develop how to control the spin states ...

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Section: Iησsupporting

confidence: 55%

Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom — Implications for an Excitonic Insulator —

et al. 2016

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“…A diamagnetic to paramagnetic transition at ∼100 K has been observed in bulk LaCoO 3 and discussed as a spin crossover from a low-spin state (LS, S = 0) to a high-spin state (HS, S = 2) or, alternatively, to an intermediate-spin state (IS, S = 1) [1][2][3][4][5][6]. Longrange ferromagnetic order has been observed in epitaxially strained LaCoO 3 thin films [7][8][9][10][11], which implies that these LaCoO 3 thin films are ferromagnetic insulators for potential application in spintronic devices and therefore of technological relevance [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…The ferromagnetic order in LaCoO 3 films is still under debate. It was initially described as being caused by the exchange interaction between LS and HS Co 3+ ions [7][8][9][10]. Fuchs et al proposed that the ferromagnetism of the LaCoO 3 thin films is caused by the Co-O-Co bond angle change because no bond length difference has been found from extended x-ray absorption fine structure (EXAFS) measurements [7,8].…”

Section: Introductionmentioning

confidence: 99%

Low-energy orbital excitations in strained LaCoO3 films

et al. 2019

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We present 90 meV resolved Co 2p3d resonant inelastic x-ray scattering linear dichroism spectra of strained LaCoO 3 films and a LaCoO 3 single crystal. A polarization-dependent low-energy excitation is observed at ∼0.2 eV on the tensile-strained LaCoO 3 /SrTiO 3 film, while it is not observed in either bulk LaCoO 3 or the compressive-strained LaCoO 3 /LaAlO 3 film. Guided by cluster calculations, we are able to distinguish the spin-state manifolds close to their transition point of Co 3+ ions in LaCoO 3 systems. Through a polarization analysis, we show that the spin state can easily flip from a low-spin 1 A 1g state in an octahedral symmetry to the high-spin 5 B 2g or 5 E g states with a small tetragonal distortion. A mixture of spin states suggests that the high-spin Co 3+ plays an important role in long-range ferromagnetic order on both tensile-and compressive-strained LaCoO 3 films.

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“…Many of the complex oxides and rare earth, transition‐metal perovskites in particular, are known for exhibiting a variety of electric and magnetic properties . Among them, the rare earth nickelates ( R NiO 3 , where R is a trivalent rare earth ion) have attracted much attention as model systems for the metal‐insulator transition (MIT) .…”

Section: Introductionmentioning

confidence: 99%

Interfacial Octahedral Manipulation Imparts Hysteresis‐Free Metal to Insulator Transition in Ultrathin Nickelate Heterostructure

Dong

Luo

et al. 2019

Adv Materials Inter

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electric and magnetic properties. [1][2][3][4] Among them, the rare earth nickelates (RNiO 3 , where R is a trivalent rare earth ion) have attracted much attention as model systems for the metal-insulator transition (MIT). [5][6][7][8] Catalan [9] summarized the results for RNiO 3 with a phase diagram showing that the nickelates are generally orthorhombic metals above the MIT temperature (T MI ) and monoclinic insulators below T MI. The strong relationship between structure and electronic properties has led to the development of several methods for modulating the MIT of RNiO 3 , e.g., strain engineering, [10] chemical doping, [11] and multilayer fabrication, [5] suggesting an array of applications in electronic and optical devices with controllable switching characteristics.The origin of the MIT has long been a subject of interest in the condensed matter sciences, and several models have been proposed. [12,13] A key parameter is the Ni-O-Ni bond angle (ϴ), which is known to affect T MI : a 180° angle maintains the 3d-2p-3d orbital overlap, resulting in metallic properties, whereas smaller angles lead to Much like epitaxial strain, engineering oxygen octahedral rotations (OORs) in perovskite oxide thin films can be a powerful means of manipulating their physical and chemical properties. Here, it is demonstrated that the fundamental character of the metal-insulator transition (MIT) can be sensitively controlled by the structure of the oxygen sublattice for NdNiO 3 thin films grown epitaxially on NdGaO 3 (110) substrates. The MIT is sharp and hysteretic for a Ni-O-Ni bond angle of 154.0° (6 nm thick film) like the bulk behavior, while it is diffuse and largely nonhysteretic for a bond angle of 149.5° (3 nm thick film), stemming from the smaller bond angle of the NdGaO 3 substrate. Using synchrotron X-ray diffraction to quantify the geometric framework of the oxygen sublattice, it is found that the influence of the substrate OORs propagates and decays after a few nanometers into the ultrathin film. The sublattice structure in the 6 nm thick film is similar to that for bulk NdNiO 3 , leading to the sharp and hysteretic MIT.

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Strain-sensitive spin-state ordering in thin films of perovskiteLaCoO3

Cited by 34 publications

References 36 publications

Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom — Implications for an Excitonic Insulator —

Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom — Implications for an Excitonic Insulator —

Low-energy orbital excitations in strained LaCoO3 films

Interfacial Octahedral Manipulation Imparts Hysteresis‐Free Metal to Insulator Transition in Ultrathin Nickelate Heterostructure

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