Evidence of exchange bias effect and surface spin glass ordering in electron doped Sm0.09Ca0.91MnO3 nanomanganites

Abstract

We report here the magnetic properties of slightly electron-doped Sm1−xCaxMnO3 manganites with the doping level of x = 0.91. Exchange bias effect has been observed in the nanomanagnites system and can be tuned by the strength of cooling field. Magnetic training effect as well as systematic shift of vertical and horizontal magnetic hysteresis loops as a function of temperature and cooling field clearly indicate the exchange bias effect. Low field dc magnetization and frequency dependent ac susceptibility results of nanomanganites suggest the onset of glassy like phase at ∼109 K. We also find spin glass like slow relaxation of magnetization, aging, and memory phenomena in the nanometric sample compared to its bulk counterpart. The enhancement of this glassy phase has been argued to be due to the modification of the phase separated state on size reduction. Magnetic training effect has been explained through the spin relaxation model. A phenomenological core-shell type model has been ascribed to an exchange coupling between the glassy ferromagnetic shell and antiferromagnetic core of Sm0.09Ca0.91MnO3 nanomanganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of this nanomanganite may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.