Ferromagnetic thin film and spin current (4) - Power dependence -

Line shape of an electromotive force (emf) spectrum using the spin pumping effect by ferromagnetic resonance (FMR) is regarded as the convoluted spectrum consisted the two emf components, i.e. the inverse spin-Hall emf (V_ISHE) and the amomalous Hall emf (V_AHE). It is known that this is expressed in eq. (1)[1]

Especially, the anomalous Hall effect makes the shape change according to the way of affection of the electric component of microwaves and the properties of samples. Therefore, it is necessary to analyze the obtained spectrum and to distinguish the mixed components by eq.(1). It makes possible to elucidate the effect of the pure spin current.

The power dependence of microwave on FMR and the ISHE (V_ISHE) 

V_obs. (Fig. 1) shows is an obtained V_emf spectrum by an experiment. V_ISHE and V_AHE were divided by fitting using eq. (1) after conversion of obtained differential spectrum (V_obs.) to an integrated one because conventional FMR method adopted a magnetic field modulation scheme.
As shown in Fig. 2, FMR spectra (Fig. 2 (a)) are proportional to the square root of the irradiated microwave power. On the other hand, V_ISHE spectra (Fig. 2 (b)) are proportional to the irradiated microwave power[2].

Fig. 1　Spectral deconvolution of V_emf spectrum.

Fig. 2　The irradiated power dependence of FMR spectra and V_ISHE spectra.

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