Obtaining thermal parameters based in the analysis only on the amplitude or phase of the photoacoustic (PA) signal from photothermal measurements is useful and valid once classical theoretical expectations are that the same parameters are contained in the photoacoustic signal. This work studies the issue of disagreement between experimentally measured amplitude and phase for AISI 316 samples with the expected theoretical result from the classical model. The results of the thermal parameters obtained from individual amplitude analysis are inconsistent with phase analysis. This work aims to show a way to get a unique value of thermal parameters from simultaneous analysis of the amplitude and phase of the PA signal. Also, the fractional models were applied to improve the fit of experimental data and provided results closed with the expected thermal diffusivity value.