Abstract
We present a muon spin relaxation study of the Mott transition in using two independent control parameters: (i) pressure to tune the electronic bandwidth and (ii) Ni substitution on the Co site to tune the band filling. For both tuning parameters, the antiferromagnetic insulating state first transitions to an antiferromagnetic metal and finally to a paramagnetic metal without undergoing any structural phase transition. under pressure displays minimal change in the ordered magnetic moment until it collapses abruptly upon entering the antiferromagnetic metallic state at . In contrast, in the Ni-doped system steadily decreases with increasing until the antiferromagnetic metallic region is reached at . In both cases, significant phase separation between regions with static magnetic order and paramagnetic/nonmagnetic regions develops when approaching or , and the antiferromagnetic metallic state is characterized by weak, random, static magnetism in a small volume fraction. No dynamical critical behavior is observed near the transition for either tuning parameter. These results demonstrate that the quantum evolution of both the bandwidth- and filling-controlled metal-insulator transition at zero temperature proceeds as a first-order transition. This behavior is common to magnetic Mott transitions in and , which are accompanied by structural transitions without the formation of an antiferromagnetic metal phase.
- Received 21 January 2019
DOI:https://doi.org/10.1103/PhysRevMaterials.3.045001
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