High-Frequency Magnetic Properties of Manganites La1−xSrxMnO3

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.