Tuning of intrinsic antiferromagnetic to ferromagnetic ordering in microporous α-MnO2 by inducing tensile strain.

By employing first principles density functional calculations, we investigated an α-MnO2 compound with a tunnel framework, which provides an eminent platform to alter the intrinsic antiferromagnetic (AFM) to ferromagnetic (FM) ordering, through the introduction of chemical or mechanical tensile strain. Our calculations further showed that the strength of FM ordering increases until 10% triaxial tensile strain. Since long range FM ordering is induced, it is realized to be superior as compared to the experimentally observed short-range FM ordering in oxygen-deficient compound. The driving force behind this superior effect is understood from the unusual electron occupancy in Mn atoms as a result of tetrahedral distortion in the MnO6 octahedra and an increase in the sp3 character of the oxygen atoms. Thus, the α-MnO2 compound belongs to a class of materials that exhibit good potential for piezomagnetic applications.