With recent developments in heat assisted magnetic recording (HAMR), there is growing intense interest in understanding the thermal-optical properties of the HAMR media. We study the phase change of the optical beam as it reflects from a FePt thin film under strong laser irradiation by carrying out close-aperture reflection Z-scan experiments. It is found that the far field spatial distribution of the reflected beam is sensitively dependent on the thermal field distribution in the media. We also carry out a temperature dependent pump-probe experiment to study the variation of the differential thermoreflection signal with different media temperature. It is found that the differential signal is sensitively dependent on the media temperature. The present studies show potential to enable noncontact temperature measurement of HAMR media and detect the spatial distribution of the thermal field in the HAMR media.