Penetration of High-Frequency Electromagnetic Field through Bulk Samples of La 1 - x Sr x MnO 3

Penetration of radio-frequency electromagnetic field through bulk samples of La 1 - x Sr x MnO 3 ( 0.33 ≤ x ≤ 0.60 ) manganites has been studied in the frequency range from 20 kHz to 30 MHz at temperatures from 300 to 400 K, which includes the temperature of the magnetic phase transition of some investigated com- positions. It has been shown that, in spite of the differences in the static properties, the dynamic properties of the investigated compositions of these manganites are similar; the differences are mainly pronounced at fre- quencies higher than 1 MHz. In the ferromagnetic range, significant changes in the transmission coefficient have been observed for all compositions upon magnetization. The magnitudes of the initial dynamic magnetic permeability have been estimated. The changes in the transmission coefficient in the ferromagnetic region are mainly caused by changes in the dynamic magnetic permeability rather than by magnetoresistance. It is shown that in the paramagnetic temperature range the magnitude of the dynamic reversible permeability exceeds unity for all compositions, which supports the assumption on the retention of local magnetic ordering.