Abstract
Upconverting particles like Yb and Er-doped NaYF(4) are known to heat up after illumination with light at pump wavelength due to inefficient upconversion processes. Here we show that NaYF(4) particles which have been co-doped not only with Yb and Er but also Fe improves the photothermal conversion efficiency. In addition, we show for the first time that alternating magnetic fields also heat up the ferromagnetic particles. Thereafter we show that a combination of optical and magnetic stimuli significantly increases the heat generated by the particles.