Abstract
We observe a disappearance of the magnetization plateau and a striking change of the magnetic configuration under a moderate doping of the model triangular antiferromagnet . The reason is an effective lifting of degeneracy of mean-field ground states by a random potential of impurities, which compensates, in the low-temperature limit, the fluctuation contribution to free energy. These results provide a direct experimental confirmation of the fluctuation origin of the ground state in a real frustrated system. The change of the ground state to a least collinear configuration reveals an effective positive biquadratic exchange provided by the structural disorder. On heating, doped samples regain the structure of a pure compound, thus allowing for an investigation of the remarkable competition between thermal and structural disorder.
- Received 29 March 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.047204
© 2017 American Physical Society