MAGNETIC PROPERTIES OF La0.67Ca0.33(CoxMn1-x)O3

Marián Mihalik – Slavomír Maťaš – Mária Zentková – Gerhard Gritzner

   Detailed study of temperature dependencies of AC susceptibility, magnetization and electrical resistance was performed on La_0.67Ca_0.33(Mn_1-xCo_x)O₃ ceramics for x = 0.01, 0.03, 0.06, 0.1, 0.15. All compounds undergo the paramagnetic-ferromagnetic phase transition between 240 K, and 60 K. Basic magnetic characteristics, like the Curie temperature and the saturated magnetization, decrease with Co-substitution Very weak frequency dependence of the peak in AC susceptibility χ"(T), hysteretic behaviour between zero-field-cooled magnetization regime and field-cooled magnetization regime are typical features of all compounds. Anomalies in electrical resistance connected with the ferromagnetic transition at the Curie temperature, the insulator-metal transitions and the re-entrant metal-isolator transition are field dependent pointing to magnetic origin of these transitions. The colossal magneto-resistance was observed for all compounds. Sintering in different atmosphere (O₂ or Ar) affects electrical resistance significantly.

Keywords: mixed-valence perovskite manganese oxides, magnetic properties, colossal magneto-resistance

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