Role of lattice structure and breaking of antiferromagnetic spin order in enhancement of ferromagnetic, electronic, and magneto-electric properties in Fe$_{2-x}$Sc$_x$O$_3$ system

Abstract: The strategy of breaking AFM ground state of alpha-Fe2O3 by doping non-magnetic Sc3+ (3d0) ions at the Fe3+ (3d5) sites has been used to understand modified lattice-structure, magnetic spin order, and charge-spin coupling in Fe$_{2-x}$Sc$_x$O$_3$ system ($x =$ 0.2, 0.5, 1.0). The material has been stabilized in single-phased (rhombohedral $\alpha$-Fe$_2$O$_3$) or mix-phased (rhombohedral alpha-Fe$_2$O$_3$ and cubic Sc$_2$O$_3$-types) structures by varying the Sc content and heat treatment temperature. Neutron diffraction confirmed magnetic moment approximately 2.75-4.68 Bohr-magneton per Fe site and spin reorientation from in-plane to out of plane direction below the Morin transition approximately 260 K. The material showed magnetic coercivity (0.2 to 6 kOe). The electrical properties transformed from insulating state (conductivity 10-14-10-10 S/cm and polarization 0.5-2 micro-C/cm$^2$) to high conductive state (conductivity approximately 10-10 -10-7 S/cm and polarization greater than 2 micro-C/cm$^2$) above Morin transition. The material at 300 K produced the maximum current density 20-95 micro-A/cm$^2$, ferroelectric polarization 2.7-15.6 micro-C/cm$^2$, ME voltage up to 5 mV with coupling coefficient 0.53 mV/Oe/cm and huge negative magnetoconductance up to 90%. The results in the present hematite based canted ferromagnetic materials are expected to be useful for applying in low power spintronic devices.