Tunable magnetic order in Fe-Mg co-doped montmoril- lonite nano-clay interfaced with amino acids.

The present study investigates the tunable magnetic order as well as the electrostatic and magnetic interactions due to the adsorption of the amino acids (AA) on the insulating montmorillonite (MMT) nano-clay in vacuum and in aqueous medium using the first principle density functional theory (DFT). A single layer MMT clay of thickness 0.68 nm has been co- doped with impurity atoms, Fe(II) and Mg(II), each of concentration 12.5 %. Our calculated values of interaction energies suggest that the water molecules enhances the binding affinity of AA molecules due to the formation of a strong hydrogen bonding with substantial charge transfer between AA molecules (charge donor) and nano-clay (charge acceptor). We also predicted the possible transition in magnetic orders (ferromagnetism, antiferromagnetism, and ferrimagnetism) due to adsorption of AA molecules while going from vacuum to aqueous medium which has not been reported yet. Such kind of study possess potential applications in tissue engineering, pharmacology, magnetic resonance imaging, and chemical engineering.