Abstract
We study the structural and magnetic orders in electron-doped by high-resolution synchrotron x-ray and neutron scatterings. Upon Ni doping , the nearly simultaneous tetragonal-to-orthorhombic structural () and antiferromagnetic () phase transitions in are gradually suppressed and separated, resulting in with increasing , as was previously observed. However, the temperature separation between and decreases with increasing for , tending toward a quantum bicritical point near optimal superconductivity at . The zero-temperature transition is preempted by the formation of a secondary incommensurate magnetic phase in the region , resulting in a finite value of above the superconducting dome around . Our results imply an avoided quantum critical point, which is expected to strongly influence the properties of both the normal and superconducting states.
- Received 29 March 2013
DOI:https://doi.org/10.1103/PhysRevLett.110.257001
© 2013 American Physical Society