Spin transitions in La0.7 Ba0.3CoO3 thin films revealed by combining Raman spectroscopy and X-ray diffraction

International audienceIn cobaltite, the spin states transitions of Co3þ/4þ ions govern the magnetic and electronic conductionproperties. These transitions are strain-sensitive and can be varied using external parameters, includingtemperature, hydrostatic pressure, or chemical stresses through ionic substitutions. In this work,using temperature dependent Raman spectroscopy and X-ray diffraction, the epitaxial strain effectson both structural and vibrational properties of La0.7 Ba0.3 CoO3 (LBCO) cobaltite thin films areinvestigated. All Raman active phonon modes as well as the structure are found to be stronglyaffected. Both Raman modes and lattice parameter evolutions show temperature changes correlatedwith magnetic and electronic transitions properties. Combining Raman spectroscopy and X-ray diffractionappears as a powerful approach to probe the spin transition in thin film cobaltite. Our resultsprovide insight into strong spin-charge-phonon coupling in LBCO thin film. This coupling manifestsas vibrational transition with temperature in the Raman spectra near the ferromagnetic spin orderedtransition at 220K