Enhanced tunneling magnetoresistance and high-spin polarization at room temperature in a polystyrene-coatedFe3O4granular system

Abstract

Polystyrene-coated ${\mathrm{Fe}}_3{\mathrm{O}}_4$ nanoparticles through surface engineering exhibit an intergranular tunneling magnetoresistance (MR) ratio of 22.8% at room temperature and a maximum MR of 40.9% at $110\mathrm{K}$. The drastic enhancement of the MR ratio clearly suggests that there is high degree of spin polarization even at room temperature for half metallic ${\mathrm{Fe}}_3{\mathrm{O}}_4$. The estimated spin polarization $P$ is about 54% and 83% at room temperature and $110\mathrm{K}$, respectively.