Left-handed properties of manganite-perovskites La 1-x Sr x MnO 3 at various dopant concentrations

The experimental study of Double Negative (DNG) state of electromagnetic wave propagating in lanthanum manganite-perovskites doped with strontium La1-xSrxMnO3 is provided firstly below individual Curie temperatures (in ferromagnetic metal state (FM) for La1-xSrxMnO3). Various dopant concentrations are considered for ceramic specimens: x = 0.15; 0.225; 0.3; 0.45; 0.6. It is shown that dependence of the DNG-peak intensity on dopant concentration is sharply non-monotone with maximum at the dopant concentrations x = 0.225 – 0.3. This behaviour follows the change of Curie temperature with increase of dopant concentration in such substances. The obtained dependence of DNG peak intensity supports the opinion concerning the role of disorder in highly doped manganite-perovskite magnetic ceramics under study.