Sample thickness dependence of giant magnetoimpedance under low fields for La_(0.67)Sr_(0.33)Mn_(0.98)Co_(0.02)O_3 manganites

摘要

The La_(0.67)Sr_(0.33)Mn_(0.98)Co_(0.02)O_3 plate sintered at 1250 °C shows a low field magnetoresistance (LFMR) effect under fields H<4.6kOe. However, the DC magnetoresistance AR/R0 is very small, only -1.84% under H=4.6 kOe. The character of helical growth was observed on grain surface of La_(0.67)Sr_(0.33)Mn_(0.98)Co_(0.02)O_3 phase. The LFMR is connected with the interface of grain or grain boundary, while the giant magnetoimpedance under low fields for La_(0.67)Sr_(0.33)Mn_(0.98)Co_(0.02)O_3 sintered plates strongly depends upon the plate thickness. With an increase of sample thickness, the magnetoimpedance increases and the frequency, where the maximum magnetoimpedance occurs, shifts to low frequencies.