Optical and magneto‐optical properties of pulsed laser‐deposited thulium iron garnet thin films

This work presents a combined optical and magneto‐optical spectroscopic study of thulium iron garnet (Tm3Fe5O12, TmIG) films on substituted gadolinium gallium garnet (Gd2.6Ca0.4Ga4.1Mg0.25Zr0.65O12, sGGG) substrates. Spectroscopic ellipsometry, transmission spectroscopy, magneto‐optical Kerr effect spectroscopy and Raman spectroscopy results are presented for TmIG films with a thickness in the range from 20 to 300 nm grown on sGGG by pulsed laser deposition. The complex dielectric functions of TmIG and sGGG are determined and compared with previously published results for bulk yttrium iron garnet and GGG, respectively. The magneto‐optical spectroscopy corroborated with Raman spectroscopy sheds light on strain‐induced changes as a function of TmIG film thickness. The optical and magneto‐optical properties of Tm3Fe5O12 films grown on substituted gadolinium gallium garnet were assessed to determine the thickness dependence of the complex dielectric functions and of the magnetic anisotropy and to shed light on epitaxy‐induced strain. Spin‐polarized density functional band structure calculations allowed to quantify the strain.