Enhanced grain surface effect on magnetic properties of nanometric La0.7Ca0.3MnO3 manganite : Evidence of surface spin freezing of manganite nanoparticles - Condensed Matter > Materials ScienceReport as inadecuate




Enhanced grain surface effect on magnetic properties of nanometric La0.7Ca0.3MnO3 manganite : Evidence of surface spin freezing of manganite nanoparticles - Condensed Matter > Materials Science - Download this document for free, or read online. Document in PDF available to download.

Abstract: We have investigated the effect of nanometric grain size on magneticproperties of single phase, nanocrystalline, granular La0.7Ca0.3MnO3 LCMOsample. We have considered core-shell structure of our LCMO nanoparticles,which can explain its magnetic properties. From the temperature dependence offield cooled FC and zero-field cooled ZFC dc magnetization DCM, themagnetic properties could be distinguished into two regimes: a relatively hightemperature regime T > 40 K where the broad maximum of ZFC curve at T = Tmaxis associated with the blocking of core particle moments, whereas the sharpmaximum at T = TS is related to the freezing of surface shell spins. Theunusual shape of M H loop at T = 1.5 K, temperature dependent feature ofcoercive field and remanent magnetization give a strong support of surface spinfreezing that are occurring at lower temperature regime T < 40 K in this LCMOnanoparticles. Additionally, waiting time tw dependence of ZFC relaxationmeasurements at T = 50 K show weak dependence of relaxation rate St on twand dM-dlnt following a logarithmic variation on time. Both of these featuresstrongly support the high temperature regime to be associated with the blockingof core moments. At T = 20 K, ZFC relaxation measurements indicates theexistence of two different types of relaxation processes in the sample withSt attaining a maximum at the elapsed time very close to the wait time tw =1000 sec, which is an unequivocal sign of glassy behavior. This age-dependenteffect convincingly establish the surface spin freezing of our LCMOnanoparticles associated with a background of superparamagnetic SPM phase ofcore moments.



Author: P. Dey, T. K. Nath, P. K. Manna, S. M. Yusuf

Source: https://arxiv.org/







Related documents