Signatures of the spin-phonon coupling in alloys

Raman scattering spectra of Fe 1 + y Te 1 − x Se x (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 A 1 g and B 1 g 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.