Abstract
Magnetic fluctuations in transition metal oxides are a subject of intensive research because of the key role they are expected to play in the transition from the Mott insulator to the unconventional metallic phase of these materials, and also as drivers of superconductivity. Despite much effort, a clear link between magnetic fluctuations and the insulator-to-metal transition has not yet been established. Here we report the discovery of a compelling link between magnetic fluctuations and the insulator-to-metal transition in Ca(Ir1−xRux)O3 perovskites as a function of the substitution coefficient x. We show that when the material turns from insulator to metal, at a critical value of x ~ 0.3, magnetic fluctuations tend to change their character from antiferromagnetic, a Mott insulator phase, to ferromagnetic, an itinerant electron state with Hund’s orbital coupling. These results are expected to have wide-ranging implications for our understanding of the unconventional properties of strongly correlated electrons systems.
Highlights
Of the chemical substitution, x = 0.3
We have investigated the role of the dynamic magnetism in the metal-insulator transition process in the family of strongly correlated perovskite compounds Ca(Ir1−xRux)O3
We have shown that the insulator-to-metal transition is accompanied by unambiguous magnetic fluctuations as a function of the chemical substitution coefficient x
Summary
This observation is consistent with the dynamic susceptibility measurements where strong magnetic fluctuations, as depicted by temperature and frequency dependences of χ′′ in Fig. 3, persist to higher temperature in x = 0.8 composition, compared to x = 1 In both cases, magnetic ions are found to fluctuate at both the short and the long time scales. Beyond mean field theory, are expected to wash out long-range ferromagnetism, while preserving strong ferromagnetic fluctuations and, the metallic character of the state This is precisely what we observe, with the metal insulator transition occurring at the relatively small value of substitution, x = 0.3, and a concomitant change in the character of the magnetic fluctuations from static antiferromagnetic to tending to dynamical ferromagnetic.
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