  We report dynamical magnetotransport in a ferromagnetic metallic oxide,
La0.7Sr0.3MnO3 using the ac impedance technique. The temperature dependence of
the ac resistance(R) and the inductive reactance (X) of the complex impedance
(Z = R+jX) under different dc bias magnetic fields (Hdc = 0-1 kOe) were studied
for different frequencies f = 0.1 to 5 MHz of alternating current. The zero
field R, which decreases smoothly around the Curie temperature TC for f = 100
kHz, transforms into a peak for f = 0.5-5 MHz. The peak decreases in amplitude,
broadens and shifts downward in temperature as the bias field increases. A huge
ac magnetoresistance (= 45 % at f = 2 MHz) in a field of Hdc = 1 kOe is found
and we attribute it to the magnetic field- induced enhancement in the skin
depth and concomitant suppression of magnetic fluctuations near TC. Our study
suggests that radio frequency magnetotransport provides an alternative strategy
to enhance the magnetoresistance and probe the spin-charge coupling in
manganites.
