We determine the phase diagram of ${\mathrm{LaFe}}_{1-x}{\mathrm{Co}}_x\mathrm{AsO}$ 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 ${\mathrm{LaFe}}_{1-x}{\mathrm{Co}}_x\mathrm{AsO}$ are identical to those in $\mathrm{Ba}{\left({\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x\right)}_2{\mathrm{As}}_2$, suggesting that nematicity in LaFeAsO is a result of the fluctuating spin density wave as well.

Close

PrevNext

View figure in article

• Nematic order
• Superconductivity
• Pnictides
• Nuclear magnetic resonance