Abstract
The perovskite antiferromagnetic insulator undergoes at ambient pressure a metal-to-insulator transition at which is associated with a simultaneous orthorhombic-to-monoclinic distortion, leading to charge disproportionation. We have investigated the change of the structural and magnetic properties of with pressure (up to ) across its quantum critical point (QCP) using low-temperature synchrotron angle-resolved x-ray diffraction and nuclear forward scattering of synchrotron radiation, respectively. With increasing pressure, we find that after a small increase of () and the induced magnetic hyperfine field at the nucleus (), both and are strongly reduced and finally disappear at , indicating a magnetic QCP at . The analysis of the structural parameters up to 10.5 GPa reveals no change of the lattice symmetry within the experimental resolution. Since the pressure-induced insulator-to-metal transition occurs at , this result implies the existence of an antiferromagnetic metallic state between 6 and 10.5 GPa. We further show from the analysis of the reported high-pressure electrical resistance data on at low temperatures that in the vicinity of the QCP the system behaves as non-Fermi-liquid, with the resistance changing as , with , whereas it becomes a normal Fermi liquid, , for pressures above . On the basis of the obtained data, a magnetic phase diagram in the () space is suggested.
- Received 20 February 2015
- Revised 28 April 2015
DOI:https://doi.org/10.1103/PhysRevB.91.195148
©2015 American Physical Society