Effect of phase separation induced supercooling on magnetotransport properties of epitaxial La5/8−yPryCa3/8MnO3 (y≈0.4) thin film

Abstract

Thin films of La5/8-yPryCa3/8MnO3 (y0.4) have been grown on single crystal SrTiO3 (001) by RF sputtering. The structural and surface characterizations confirm the epitaxial nature of these film. However, the difference between the -scan of the (002) and (110) peaks and the presence of pits/holes in the step-terrace type surface morphology suggests high density of defect in these films. Pronounced hysteresis between the field cool cooled (FCC) and field cooled warming (FCW) magnetization measurements suggest towards the non-ergodic magnetic state.The origin of this nonergodicity could be traced to the magnetic liquid like state arising from the delicacy of the coexisting magnetic phases, viz., ferromagnetic and antiferromagneticcharge ordered (FM/AFM-CO). The large difference between the insulator metal transitions during cooling and warming cycles (TIM C~6 4 K and TIM W~1 23 K) could be regarded as a manifestation of the nonergodicity leading to supercooling of the magnetic liquid while cooling. The nonergodicity and supercooling are weakened by the AFM-FM phase transition induced by an external magnetic field. TIM and small polaron activation energy corresponding the magnetic liquid state (cooling cycle) vary nonlinearly with the applied magnetic field but become linear in the crystalline solid state (warming cycle). The analysis of the low temperature resistivity data shows that electron-phonon interaction is drastically reduced by the applied magnetic field. The resistivity minimum in the lower temperature region of the selffield warming curve has been explained in terms of the Kondo like scattering in the magnetically inhomogeneous regime.

A comparative study on phase co-existence of $$\hbox {La}_{1/4}\hbox {Pr}_{3/8}\hbox {Ca}_{3/8}\hbox {MnO}_{3}$$ in a polycrystalline bulk and thin film

“…In the low temperature region (<50 K) the FCW curve follows the FCC curve in both cases, while the ZFC curve shows an increase in magnetization with rise in temperature. This feature in the ZFC curve of both the samples is attributed to the unblocking of moments which get blocked in a metastable state on reduction of the temperature in the absence of magnetic field [18,19]. Figure 4 presents the M-H isotherms for both the samples recorded at 5 K where the field is ramped up from 0 to 5 T and then reduced.…”