Thickness dependence of exchange coupling in (111)-oriented perovskite oxide superlattices

Jia, Yunpeng; Chopdekar, Rajesh V.; Arenholz, Elke; Liu, Zhiqi; Biegalski, Michael D.; Porter, Zachary D.; Mehta, Apurva; Takamura, Yayoi

doi:10.1103/physrevb.93.104403

Cited by 18 publications

(23 citation statements)

References 54 publications

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“…With the TEY measurements, the Mn-XA/XMCD signal emanates primarily from the portion of the LSMO sublayer in proximity to the top LSMO/LSCO interface, and the signal could not be detected above the noise floor for the m > 12 SLs. For the m ⩽ 12 SLs, the interface-sensitive Mn-XA spectra resembles that of the LSCMO film and differs from LSMO [40][41][42][43][44]. However, as with the Co-XMCD spectra, the spectral shape of the Mn-XMCD curves remains unchanged, indicating that the magnetically active Mn 3+ /Mn 4+ ions remain largely as in the thick LSMO film though they are broken up by a higher concentration of Mn 4+ ions.…”

Section: Maximum Of Dρ(t) Dtmentioning

confidence: 95%

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

Chopdekar¹,

Malik²,

Kane³

et al. 2017

J. Phys.: Condens. Matter

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TitleEngineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior IntroductionDue to the strong coupling between the charge, spin, orbital, and lattice degrees of freedom, perovskite oxides with the chemical formula ABO 3 display a wide range of technologically relevant properties including ferromagnetism, ferroelectricity, and superconductivity [1]. Modern thin film growth techniques such as pulsed laser deposition (PLD) offer atomic scale control of the chemical composition, structural properties, and thickness of sublayers, and therefore have enabled the engineering of artificial composite materials which display emergent properties which differ from those of the constituent materials [2,3]. In these systems, interfacial interactions such as structural effects (i.e. breaking the 3D symmetry of the material, epitaxial strain, and modifications of the inherent BO 6 octahedral tilts/rotations), chemical effects (i.e. atomic intermixing), electronic effects (i.e. electronic/orbital reconstruction, charge transfer), and magnetic effects (i.e. exchange interactions, finite size effects associated with 2D layers) become important [4,5]. The competition between multiple interactions places a great challenge on our ability to understand and predict the resulting functional properties, and ultimately to exploit the emergent properties in applications.In this work, we explore the extent of interfacial interactions occurring in superlattices (SLs) composed of two ferromagnetic (FM) and metallic perovskite oxides, La 0.7 Sr 0. AbstractThe extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La 0.7 Sr 0.3 MnO 3 /La 0.7 Sr 0.3 CoO 3 ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5-6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers. The saturation magnetization and coercivity depends sensitively on the sublayer thickness due to the length scale of this interfacial effect. For larger sublayer thicknesses, the La 0.7 Sr 0.3 MnO 3 and La 0.7 Sr 0.3 CoO 3 sublayers are magnetically decoupled, displaying two independent magnetic transitions with little sublayer thickness dependence. These results demonstrate how interfacial phenomena at perovskite oxide interfaces can be used to tailor their functional properties at the atomic scale.

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Section: Maximum Of Dρ(t) Dtmentioning

confidence: 95%

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

Chopdekar¹,

Malik²,

Kane³

et al. 2017

J. Phys.: Condens. Matter

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“…Interfacial and confinement effects in heterostructures grown along the perovskite-(111) orientation are much less studied. 24,29,33,34 Interestingly, in a thin film with a thickness of two monolayers (MLs) of LNO grown along this orientation, the Ni atoms form a buckled honeycomb lattice; such a heterostructure was predicted to host novel topological phases which are yet to be found experimentally. [35][36][37][38] The recent realization of high quality heterostructures that combine LNO with thin insulating ferromagnetic LaMnO 3 (LMO) layers along the (111) direction and exhibit unexpected phenomena is an example of the novel physics found in this type of heterostructures.…”

confidence: 99%

Electronic structure of buried LaNiO3 layers in (111)-oriented LaNiO3/LaMnO3 superlattices probed by soft x-ray ARPES

et al. 2017

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Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy we report electronic structure measurements of (111)oriented [LaNiO3/LaMnO3] superlattices and LaNiO3 epitaxial films. For thin films we observe a 3D Fermi surface with an electron pocket at the Brillouin zone center and hole pockets at the zone vertices. Superlattices with thick nickelate layers present a similar electronic structure. However, as the thickness of the LaNiO3 is reduced the superlattices become insulating. These heterostructures do not show a marked redistribution of spectral weight in momentum space but exhibit a pseudogap of ≈ 50 meV. Main TextWith the advancement of synthesis techniques it is possible nowadays to control the growth of transition metal oxide (TMO) epitaxial heterostructures at the unit cell level. The realization of such heterostructures have resulted in the discovery of fascinating phenomena as a consequence of the confinement of strongly correlated electrons in ultrathin high quality layers. [1-3] Since these thin layers are embedded in heterostructures, interfacial phenomena such as charge transfer and magnetic coupling play an important role together with dimensionality in determining the ground state of the system. [4-8] The recent development of combined angle-resolved photoemission spectroscopy (ARPES) and oxide heterostructures growth setups has allowed the electronic structure of TMO heterostructures to be probed directly.

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Section: Maximum Of Dρ(t) Dtmentioning

confidence: 89%

Nanostructured complex oxides as a route towards thermal behavior in artificial spin ice systems

Chopdekar

Wynn

et al. 2017

Phys. Rev. Materials

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We have used soft x-ray photoemission electron microscopy to image the magnetization of single domain La0.7Sr0.3MnO3 nano-islands arranged in geometrically frustrated configurations such as square ice and kagome ice geometries. Upon thermal randomization, ensembles of nanoislands with strong inter-island magnetic coupling relax towards low-energy configurations. Statistical analysis shows that the likelihood of ensembles falling into low-energy configurations depends strongly on the annealing temperature. Annealing to just below the Curie temperature of the ferromagnetic film (TC = 338 K) allows for a much greater probability of achieving low energy configurations as compared to annealing above the Curie temperature. At this thermally active temperature of 325 K, the ensemble of ferromagnetic nano-islands explore their energy landscape over time and eventually transition to lower energy states as compared to the frozen-in configurations obtained upon cooling from above the Curie temperature. Thus, this materials system allows for a facile method to systematically study thermal evolution of artificial spin ice arrays of nano-islands at temperatures modestly above room temperature.

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Thickness dependence of exchange coupling in (111)-oriented perovskite oxide superlattices

Cited by 18 publications

References 54 publications

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

Engineered superlattices with crossover from decoupled to synthetic ferromagnetic behavior

Electronic structure of buried LaNiO3 layers in (111)-oriented LaNiO3/LaMnO3 superlattices probed by soft x-ray ARPES

Nanostructured complex oxides as a route towards thermal behavior in artificial spin ice systems

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