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Register a new userHeterointerface engineered electronic and magnetic phases of NdNiO3 thin films
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Mott physics is characterized by an interaction-driven metal-to-insulator transition in a partially filled band. In the resulting insulating state, antiferromagnetic orders of the local moments typically develop, but in rare situations no long-range magnetic order appears, even at zero temperature, rendering the system a quantum spin liquid. A fundamental and technologically critical question is whether one can tune the underlying energetic landscape to control both metal-to-insulator and Neel transitions, and even stabilize latent metastable phases, ideally on a platform suitable for applications. Here we demonstrate how to achieve this in ultrathin films of NdNiO3 with various degrees of lattice mismatch, and report on the quantum critical behaviours not reported in the bulk by transport measurements and resonant X-ray spectroscopy/scattering. In particular, on the decay of the antiferromagnetic Mott insulating state into a non-Fermi liquid, we find evidence of a quantum metal-to-insulator transition that spans a non-magnetic insulating phase.
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We have synthesized epitaxial NdNiO$_{3}$ ultra-thin films in a layer-by-layer growth mode under tensile and compressive strain on SrTiO$_{3}$ (001) and LaAlO$_3$ (001), respectively. A combination of X-ray diffraction, temperature dependent resistivity, and soft X-ray absorption spectroscopy has been applied to elucidate electronic and structural properties of the samples. In contrast to the bulk NdNiO$_{3}$, the metal-insulator transition under compressive strain is found to be completely quenched, while the transition remains under the tensile strain albeit modified from the bulk behavior.
We have investigated the electronic and magnetic properties of perovskite SrRu1-xIrxO3 thin films grown by pulsed laser deposition on atomically-flat (001) SrTiO3 substrates. SrRuO3 has the properties of a ferromagnetic metal with Curie temperature 150 K. Substituting Ir for Ru in SrRuO3, films showed fully-metallic behavior and ferromagnetic ordering, although resistivity increased and the ferromagnetic TC decreased. Films with x = 0.25 underwent the metal-to-insulator transition at 75 K, and spin-glass-like ordering at 45 K with the elimination of ferromagnetic long-range ordering caused by the electron localization at the substitution sites. In ferromagnetic films, resistivity increased near-linearly with T, but in paramagnetic film (x = 0.25) resistivity increased as T3/2. Moreover, observed spin-glass-like (TSG) ordering with the negative magnetoresistance in film with x = 0.25; validates the hypothesis that (Anderson) localization favors glassy ordering at amply disorder limit. These observations provide a promising approach for future applications and of fundamental interest in 4d and 5d mixed perovskites.
We investigate the behavior of the spectral weight near the Fermi level of NdNiO3 thin films as a function of temperature across the metal-to-insulator transition (MIT) by means of ultraviolet photoelectron spectroscopy. The spectral weight was found to exhibit thermal hysteresis, similar to that of the dc conductivity. A detailed analysis of the temperature dependence reveals two distinct regimes of spectral loss close to the Fermi level. The temperature evolution of one regime is found to be independent from the MIT.
We present a comparison of the in-plane length scale over which charge and magnetism are correlated in (La0.4Pr0.6)1-xCaxMnO3 films with x = 0.33 and 0.375, across the metal to insulator transition (MIT) temperature. We combine electrical transport (resistance) measurements, x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), and specular/off-specular x-ray resonant magnetic scattering (XRMS) measurements as a function of temperature to elucidate relationships between electronic, magnetic and morphological structure of the thin films. Using off-specular XRMS we obtained the charge-charge and charge-magnetic correlation length of these LPCMO films near the MIT. The charge-magnetic correlation length (~ 12000 {AA}) for x = 0.33 was much larger (~4 times) than the charge-charge correlation length (~ 3200 {AA}) at 20 K. Whereas for x = 0.375 the charge-magnetic correlation length (~ 7500 {AA}) was smaller than the charge-charge correlation length (~ 9000 {AA}).
Nickelates are known for their metal to insulator transition (MIT) and an unusual magnetic ordering, occurring at T=T_Neel. Here, we investigate thin films of SmNiO_3 subjected to different levels of epitaxial strain. We find that the original bulk behavior (T_Neel<T_MI) is strongly affected by applying compressive strain to the films. For small compressive strains, a regime where T_Neel=T_MI is achieved, the paramagnetic insulating phase characteristic of the bulk compound is suppressed and the MIT becomes 1st order. Further increasing the in-plane compression of the SmNiO_3 lattice leads to the stabilization of a single metallic paramagnetic phase.
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