SUMMARYThe magnetic moment and lattice parameter of stoichiometric spinel lithium ferrite (Lio.5Fe2.5011) has been reliably established, respectively, as 3736 f 20G at 25OC and 8.3293 2 0.0005& at 28OC. Under 1 atmosphere of oxygen, lithium ferrite loses both oxygen and lithium oxide in increasing amounts with increasing temperature above about 950 to 1000°C. Slow cooling and annealing at a lower temperature bring about reoxidation and precipitation of a-Fe203. Rapid cooling from the sintering temperature leads to anomalously high magnetic moments and lattice parameters; lower temperature anneals and very slow cooling rates produce anomalously low moment values. Intermediate cooling procedures lead to properties intermediate between these properties.
We report perpendicular spin-wave resonance measurements in single crystal YIG films a t 77 K and several frequencies. For films of thickness 0.9 W m the SWR mode positions follow a quadratic (n2) dependence. For 0.37 pm thick films sizeable deviations appear a t n > 4. Further, these deviations increase with microwave frequency. Effects of annealing these films a t several temperatures between 700 and 1250 "C have also been studied. It is suggested that the data can be roughly understood by invoking a diffusion region, of varying magnetization, a t the YIG-substrate interface.L'article d6crit des etudes d'ondes de spin en resonance perpendiculaire B plusieurs frbquences sur des couches monocristallines d'YIG. Pour des couches d'6paisseur 0,9 um. les positions des modes de resonance suivent une loi quadratique (n2). Pour des couches d'6paisseur 0,37 pm, des deviations assez grandes apparaissent pour n > 4. De plus ces deviations augmentent avec la frequence microonde. On a aussi 6tudi6 l'effet sur ces films de recuits B diffbrentes tempdratures entre 700 et 1250 "c. On suggbre que les rbsultats peuvent Btre assez bien expliquhs en postulant une region de diffusion, d'aimantation variable, B l'interface YIG-substrat.
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