8 research outputs found
Antiferromagnetic metal phase in an electron-doped rare-earth nickelate
Long viewed as passive elements, antiferromagnetic materials have emerged as
promising candidates for spintronic devices due to their insensitivity to
external fields and potential for high-speed switching. Recent work exploiting
spin and orbital effects has identified ways to electrically control and probe
the spins in metallic antiferromagnets, especially in noncollinear or
noncentrosymmetric spin structures. The rare earth nickelate NdNiO3 is known to
be a noncollinear antiferromagnet where the onset of antiferromagnetic ordering
is concomitant with a transition to an insulating state. Here, we find that for
low electron doping, the magnetic order on the nickel site is preserved while
electronically a new metallic phase is induced. We show that this metallic
phase has a Fermi surface that is mostly gapped by an electronic reconstruction
driven by the bond disproportionation. Furthermore, we demonstrate the ability
to write to and read from the spin structure via a large zero-field planar Hall
effect. Our results expand the already rich phase diagram of the rare-earth
nickelates and may enable spintronics applications in this family of correlated
oxides.Comment: 25 pages, 4 figure
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Liberating a hidden antiferroelectric phase with interfacial electrostatic engineering.
Antiferroelectric materials have seen a resurgence of interest because of proposed applications in a number of energy-efficient technologies. Unfortunately, relatively few families of antiferroelectric materials have been identified, precluding many proposed applications. Here, we propose a design strategy for the construction of antiferroelectric materials using interfacial electrostatic engineering. We begin with a ferroelectric material with one of the highest known bulk polarizations, BiFeO3. By confining thin layers of BiFeO3 in a dielectric matrix, we show that a metastable antiferroelectric structure can be induced. Application of an electric field reversibly switches between this new phase and a ferroelectric state. The use of electrostatic confinement provides an untapped pathway for the design of engineered antiferroelectric materials with large and potentially coupled responses
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Synthesis and electronic properties of Ndn+1NinO3n+1 Ruddlesden-Popper nickelate thin films
The rare-earth nickelates possess a diverse set of collective phenomena including metal-to-insulator transitions, magnetic phase transitions, and upon chemical reduction, superconductivity. Here, we demonstrate epitaxial stabilization of layered nickelates in the Ruddlesden-Popper form Ndn+1NinO3n+1 using molecular beam epitaxy. By optimizing the stoichiometry of the parent perovskite NdNiO3, we can reproducibly synthesize the n=1-5 member compounds. X-ray absorption spectroscopy at the O K and Ni L edges indicate systematic changes in both the nickel-oxygen hybridization level and nominal nickel filling from 3d8 to 3d7 as we move across the series from n=1 to ∞. The n=3-5 compounds exhibit weakly hysteretic metal-to-insulator transitions with transition temperatures that depress with increasing order toward NdNiO3 (n=∞)
Synthesis and electronic properties of NdNiO Ruddlesden-Popper nickelate thin films
The rare-earth nickelates possess a diverse set of collective phenomena
including metal-to-insulator transitions, magnetic phase transitions, and, upon
chemical reduction, superconductivity. Here, we demonstrate epitaxial
stabilization of layered nickelates in the Ruddlesden-Popper form,
NdNiO, using molecular beam epitaxy. By optimizing the
stoichiometry of the parent perovskite NdNiO, we can reproducibly
synthesize the member compounds. X-ray absorption spectroscopy at
the O and Ni edges indicate systematic changes in both the
nickel-oxygen hybridization level and nominal nickel filling from 3 to
3 as we move across the series from to . The compounds exhibit weakly hysteretic metal-to-insulator transitions with
transition temperatures that depress with increasing order toward NdNiO (.Comment: 11 pages, 4 figures with Supplemental Informatio
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Limits to the strain engineering of layered square-planar nickelate thin films
The layered square-planar nickelates, Ndn+1NinO2n+2, are an appealing system to tune the electronic properties of square-planar nickelates via dimensionality; indeed, superconductivity was recently observed in Nd6Ni5O12 thin films. Here, we investigate the role of epitaxial strain in the competing requirements for the synthesis of the n = 3 Ruddlesden-Popper compound, Nd4Ni3O10, and subsequent reduction to the square-planar phase, Nd4Ni3O8. We synthesize our highest quality Nd4Ni3O10 films under compressive strain on LaAlO3 (001), while Nd4Ni3O10 on NdGaO3 (110) exhibits tensile strain-induced rock salt faults but retains bulk-like transport properties. A high density of extended defects forms in Nd4Ni3O10 on SrTiO3 (001). Films reduced on LaAlO3 become insulating and form compressive strain-induced c-axis canting defects, while Nd4Ni3O8 films on NdGaO3 are metallic. This work provides a pathway to the synthesis of Ndn+1NinO2n+2 thin films and sets limits on the ability to strain engineer these compounds via epitaxy
Liberating a hidden antiferroelectric phase with interfacial electrostatic engineering
Antiferroelectric materials have seen a resurgence of interest because of proposed applications in a number of energy-efficient technologies. Unfortunately, relatively few families of antiferroelectric materials have been identified, precluding many proposed applications. Here, we propose a design strategy for the construction of antiferroelectric materials using interfacial electrostatic engineering. We begin with a ferroelectric material with one of the highest known bulk polarizations, BiFeO3. By confining thin layers of BiFeO3 in a dielectric matrix, we show that a metastable antiferroelectric structure can be induced. Application of an electric field reversibly switches between this new phase and a ferroelectric state. The use of electrostatic confinement provides an untapped pathway for the design of engineered antiferroelectric materials with large and potentially coupled responses.ISSN:2375-254