Ferromagnetic Antiresonance and Giant Microwave Magneto-Impedance in Polycrystalline La_0.49Sr_0.51MnO₃

The ferromagnetic antiresonance (FMAR) phenomenon, i.e., the minimum of the microwave absorption, in polycrystalline La_0.49Sr_0.51MnO₃ is observed near Curie temperature T_C = 282K. Temperature-dependences of magnetization μ₀M are obtained from the FMAR. The results show that as
μ₀H =0, by fitting the scaling law M∝(T_C-T)^β to temperature-dependences of μ₀M at the different microwave frequencies, it yields T_C = 281.2K and β= 0.47. However, temperature-dependences of β₀M under different β₀H are not
in agreement with the scaling law. Due to FMAR, about 40% giant microwave magneto-impedance at 11.9GHz can occur under a low field μ₀H=0.03T.