High-Frequency Magnetic Properties of Manganites La_1−xSr_xMnO₃

Abstract

High-frequency (HF) magnetic properties have been studied for manganites La _1-x Sr _x MnO ₃ with Sr = 0.2-0.4. The manganites have good HF properties with the real permeability μ ₀ ' of 50-80, maximum imaginary permeability μ _max " of 22-32, and resonance frequency of 10-40 MHz. Two types of resonances are found for La _1-x Sr _x MnO ₃ : one is from domain wall and the other is from natural resonance. With increasing annealing temperature Ta, μ ₀ ' significantly increases, which is attributed to an increase of density, based on the magnetic circuit model. The frequency f _R2 of natural resonance is almost unchanged, but f _R1 of wall resonance is shifted to lower frequency that has its origin in the decrease of resistivity.