Galvanomagnetic Interactions In Ferromagnetic Resonance

A new method has been developed for studying the galvanomagnetic as well as the magnetic properties of ferromagnetic materials. The method has been applied to thin films of nickel and permalloy and has yielded results for the conductivity, magnetoresistance anisotropy, extraordinary Hall coefficient, saturation magnetization, and magnetic relaxation time in these materials at microwave frequencies. The new method consists of measuring the second harmonic signal generated by galvanomagnetic interactions when an electromagnetic wave is incident on a magnetized conducting ferromagnetic film. In a ferromagnetic material, the relationship between current density and the applied electric fields takes the usual form of Ohm's Law with second and third termis due to galvanomagnetic effects. The measurement of the microwave galvanomagnetic properties of ferromagnetic materials by the second harmonic method has an advantage over the measurement of the dc signal in that two measurements can be made - the magnitude and phase of the galvanomagnetically-induced signal. The process of extracting the material parameters from the measured data is thus greatly simplified. In addition, the method has been shown to be a sensitive probe of the state of magnetization in thin films. It can be extended to study in greater detail films with spacial variations in magnetization, as in standing spin waves, non-linearities in the magnetization at high powers, as well as galvanomagnetic effects in magnetic semiconductors or paramagnetics. (Author).