Microwave magnetoimpedance and ferromagnetic resonance in Pr0.6Sr0.4MnO3

Abstract

We report the magnetic field dependence of electrical impedance (magnetoimpedance) of a ferromagnetic Pr_0.6Sr_0.4MnO₃ sample carrying alternating current (ac) of frequency f = 1 MHz to 3 GHz measured using an impedance analyzer and broad band ferromagnetic resonance (f = 2 to 18 GHz) measured using a coplanar wave guide based spectrometer. Ac magnetoresistance is much larger than dc magnetoresistance and its sign at low magnetic fields changes from negative to positive with increasing frequency of the ac current. The field dependence of ac magnetoresistance shows a peak around H_dc = 0 for low frequencies but a double peak feature emerges at H_dc = ±H_p at higher frequencies and it shifts to higher magnetic field as the frequency of ac current increases. The field derivative of microwave power absorption measured by the broad band spectrometer shows features of ferromagnetic resonance and the resonance field increases with increasing frequency of microwave radiation following Kittel's equation for ferromagnetic resonance. A close correlation is found between the ferromagnetic resonance line shape and the positive peak in the ac magnetoresistance, which suggests the possibility of electrical detection of ferromagnetic resonance using high frequency current injected into a conducting magnetic sample.