Evidence of Surface Spin Glass Like Ordering and Exchange Bias Effect in Phase Separated Sm0.5Ca0.5MnO3 Nanomanganites

In this article, we report that the charge/orbital order state of bulk antiferromagnetic Sm0.5Ca0.5MnO3 is suppressed and confirms the appearance of weak ferromagnetism below 65 K followed by a low temperature spin glass (SG) like transition at 41 K in its nano metric counterpart. Exchange anisotropy effect has been observed in the nanomanganites and can be tuned by the strength of the cooling magnetic field (H-cool). The values of exchange bias fields (H-E), coercivity (H-C), remanence asymmetry (M-E) and magnetic coercivity (M-C) are found to strongly depend on cooling magnetic field and temperature. H-E increases with increasing H-cool but for larger H-cool, H-E tends to decrease due to the growth of finite size ferromagnetic clusters. A proposed phenomenological core-shell type model is attributed to an exchange coupling between the spin-glass like shell (surrounding) and antiferromagnetic core of Sm0.5Ca0.5MnO3 nanomanganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructured manganites may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.