Transport and electron spin resonance studies in Mo-doped LaMnO3

Abstract

We report the magnetic, electrical, thermoelectric, and magnetic resonance properties of the Mn-site doped manganite LaMn0.94Mo0.06O3. This sample undergoes an insulator-metal transition around 235 K, near the ferromagnetic Curie temperature (TC = 237 K) in zero external magnetic field. On the other hand, thermopower exhibits a maximum at TS = 258 K, which is 23 K higher than TC. This discrepancy is attributed to nucleation of ferromagnetic clusters (Griffiths phase) above TC, which is supported by the deviation of inverse susceptibility from Curie-Weiss from linear behavior below 270 K and non-linear field dependence of magnetization. The magnetic resonance spectra shows both paramagnetic and ferromagnetic resonance signals between 240 and 260 K. It is suggested that the ferromagnetic clusters enlarge in size with lowering temperature and percolate leading to long-range ferromagnetism and metallicity.