Coercivity and nanostructure in magnetic spinel Mg(Mn,Fe)2O4

Abstract

When Fe ions in the ferrimagnetic cubic MgFe2O4 are replaced by Jahn-Teller (JT)-active Mn ions, the structure evolves with two-step processes. For example, the quenched cubic MgMn1.5Fe0.5O4 becomes tetragonal and JT distorted with slow cooling. However, with further slow cooling, the clustering tendency of JT-distorted Mn ions induces the formation of a checkerboard nano-self-assembly consisting of Mn-rich (tetragonal, paramagnetic) and -poor (cubic, ferrimagnetic) rods. This morphological evolution accompanies a drastic modification of ferrimagnetic properties, e.g., the magnetic coercivity changes by ∼25. The nanocheckerboard assembly with ferrimagnetic nanorods with large shape anisotropy can be a platform for ultra high-density memory devices.