We determine the phase diagram of LaFe1−xCoxAsO single crystals by using nuclear magnetic resonance (NMR). Up to a nominal doping of x=0.03, it follows the phase diagram for F-doped polycrystals. Above x=0.03, the F-doped samples become superconducting, whereas for Co-doping the structural and magnetic transitions can be observed up to x=0.042, and superconductivity occurs only for higher doping levels and with reduced transition temperatures. For dopings up to x=0.056, we find evidence for short-range magnetic order. By means of relaxation-rate measurements, we map out the magnetic fluctuations that reveal the interplay of nematicity and magnetism. Above the nematic ordering, the spin fluctuations in LaFe1−xCoxAsO are identical to those in Ba(Fe1−xCox)2As2, suggesting that nematicity in LaFeAsO is a result of the fluctuating spin density wave as well.
@article{arxiv.2011.13641,
title = {Mapping out the spin fluctuations in Co-doped LaFeAsO single crystals by NMR},
author = {Piotr Lepucki and Raphael Havemann and Adam P. Dioguardi and Francesco Scaravaggi and Anja U. B. Wolter-Giraud and Rhea Kappenberger and Sai Aswartham and Sabine Wurmehl and Bernd Büchner and Hans-Joachim Grafe},
journal= {arXiv preprint arXiv:2011.13641},
year = {2021}
}