Electron-phonon coupling enhancement and displacive magnetostructural transition in SrCr₂ As₂ under magneto-Raman...

A Raman spectroscopy study on high quality single crystals of SrCr₂ As₂ (SCA) in the temperature T range 4 K < T < 300 K and high applied magnetic fields up to H = 9 T is presented. The chromium B _1g phonon analysis reveals two anomalous shifts in the frequency, the first below T = 250 K at H = 0 T in the saturated AFM G-type order likely due to an enhanced electron-phonon coupling by the magnetic order, whereas the second anomaly occurs above H = 4 T at T = 4 K likely as a consequence of a magnetostructural displacive transition. Renormalization of the electronic Raman spectra in both studies reveals a decrease in the electronic density of states with decreasing T and increasing H, respectively, with consequent changes in the Fermi surface, which are intrinsically related to the observed anomalies.