Measurements of the exchange stiffness of YIG films by microwave resonance techniques

Abstract

Measurements of the exchange stiffness \(D\) and the exchange constant \(A\) of Yttrium Iron Garnet (YIG) films are presented. The YIG films with thicknesses from 0.9 \(\mu\)m to 2.6 \(\mu\)m were investigated with a microwave setup in a wide frequency range from 5 to 40 GHz. The measurements were performed when the external static magnetic field was applied in-plane and out-of-plane. The method of Schreiber and Frait, based on the analysis of the perpendicular standing spin wave (PSSW) mode frequency dependence on the applied out-of-plane magnetic field, was used to obtain the exchange stiffness \(D\). This method was modified to avoid the influence of internal magnetic fields during the determination of the exchange stiffness. Furthermore, the method was adapted for in-plane measurements as well. The results obtained using all methods are compared and values of \(D\) between \((5.18\pm0.01) \cdot 10^{-17}\)T\(\cdot\)m\(^2\) and \((5.34\pm0.02) \cdot 10^{-17}\) T\(\cdot\)m\(^2\) were obtained for different thicknesses. From this the exchange constant was calculated to be \(A=(3.65 \pm 0.38)~\)pJ/m.