YIG Films Through Synthesis by Means of the Polymeric Precursor Method: Correlation Between the Structural and Vibrational Properties with Magnetic Behavior

Yttrium iron garnet (YIG, Y3Fe5 O (12)) films were synthesized from a polymeric precursor and they were deposited by spin coating onto amorphous silica substrates; where the films were annealed at T (a) = 450, 600, 700, 800, and 900 C-ay under air. Vibrational and magnetic properties of YIG films were followed by means of Raman spectroscopy, vibrant sample magnetometry (VSM), and ferromagnetic resonance (FMR), respectively. X-ray diffraction and Raman spectroscopy indicated that the YIG films are crystalline after annealing at T (a) 800 C-ay, but they are amorphous below T (a). The amorphous films have a broad Raman band to 670 cm(-1), due to higher states in the phonon state density of YIG, suggesting the existence of a short order around tetrahedral Fe3+ ions. Magnetic hysteresis measurements are indicative of a superparamagnetic behavior in amorphous YIG films and with a soft magnetic behavior in the crystalline ones. The deconvolution in FMR spectra shows that the amorphous precursor films have two different absorption modes corresponding to different sites for Fe3+ ions: the first is associated with magnetic local ordering around tetrahedral Fe3+ centers corresponding with superexchange interactions J (aa) in tetrahedral sites, while the other absorption is associated with an amorphous matrix in the paramagnetic state. Finally, FMR spectra in crystalline films show the presence of two different sites for Fe3+ ions, and that they are associated with magnetic local ordering around tetrahedral and octahedral Fe3+ centers.