Signatures of the spin-phonon coupling in Fe1+yTe1−xSexFe1+yTe1−xSex alloys

• Raman scattering spectra and lattice dynamics of the FeTeSe alloys are presented.
• A1g mode follows the standard anharmonic temperature dependence.
• B1g mode frequency (linewidth) follows magnetic susceptibility temperature dependence.

Raman scattering spectra of Fe1+yTe1−xSexFe1+yTe1−xSex (x=0, y=0.07; x=0.1, y=0.05 and x=0.4, y=0.02) alloys are measured in a temperature range between 20 K and 300 K. The A1gA1g and B1gB1g Raman active modes have been experimentally observed at energies 156 and 198 cm−1, which is in rather good agreement with the lattice dynamics calculation. The antiferromagnetic spin ordering below 70 K in Fe1.07Te leaves a fingerprint only in the B1g phonon mode linewidth and energy, whose temperature dependence follows the normalized magnetic susceptibility, indicating the presence of the spin-phonon coupling. The frequency and the linewidth of the A1g mode assume a conventional anharmonic temperature dependence in all measured samples, which is also the case for the B1g mode in the Se doped samples. The linewidth (energy) of the A1g mode decreases (increases) with doping, whereas the opposite is seen for the B1g mode.