Resumen de Microwawe Absorption Studies of Mn-based Perovskites
S.M. Bhagat, S.E. Lofrand, S.D Tyagi, M.A. Manheimer
We review recent studies of microw^ave absorption in a few prototypical manganites which exhibit colossal magnetoresistance. Ferromagnetic resonance measurements show that most bulk samples are far from homogeneous. Careful control of deposition parameters yields thin films with greatly improved homogeneity. The best films were used to observe spin wave resonances and obtain the spin wave stiffness parameter. Surface impedance measurements in zero field and applied fields show quite unexpected cross-overs from normal (ReZ oc Vp or p) to inverted (ReZ oc 1/ Vp or p) behavior. The magnetoresistance at 10 GHz is even larger than that in the dc studies. Ferromagnetic antiresonance signals are used to get colossal magnetoimpedance (60% in 60 mT) as well as demonstrate that the ferromagnetic transition is continuous (second order).
