Colossal Magnetoresistance in Potassium Doped Lanthanum Manganite: A Comparative Study of Polycrystalline Solid and Thin Film

Electrical and magnetic properties of $La_{0.82}K_{0.08}MnO_{3-\delta}$, both in polycrystalline and thin film forms, have been examined in the temperature range 1.2 to 300 K. Near the insulator-to-metal transition temperature of 260 K, the magnetoresistance values were higher for the thin film (~70%) compared to the polycrystalline sample (~35%). No magnetoresistance was observed in the thin film at low temperature. A low field magnetoresistance of 30% was observed in the temperature range 1.2–10 K in the polycrystalline sample which can be attributed to the spin dependent scattering of conduction electrons at the grain boundaries