Role of d electrons in multifunctional materials

Title : Role of d electrons in multifunctional materials

Abstract:

Multifunctional materials are of today’s quest. A class of multifunctional materials display simultaneous ordering in different dimensions like magnetism, polarization etc. They are more known as multiferroics. Quite a significant number of them are based on perovskite structures having a transition metal ion in the body centre. The electronic configuration of this central transition element play a key role in the behavior of those multiferroics. For example, those with d⁰ configuration display ferroelectricity while those with dⁿ (where n is non zero) generally display magnetic behavior. The d⁰ configuration leads to distortion of metal-oxygen bond in these perovskites and breaking of special inversion symmetry causing a local dipole moment and ferroelectricity. Often this distortion in metal-oxygen bond is caused by lone pair of electrons of  non transitional cations in the corners of the perovskite structure.BiFeO₃ (BFO) is a shining example of this kind of distortion, where the central ion Fe(III) causes magnetism but Bi(III) ions in the corner cause the polarization leading to the multiferroicity in BFO displaying both ferroelectric and antiferromagntic ordering. The symmetry breaking manifests in different kinds of ordering. Moreover, the variable valency of the central transition metal ion with d electrons manifests in redox behavior in these materials leading to various uses. We have observed such various functions in the multiferroic BFO like ferroelectric, magnetic and high specific capacitance rendering these materials useful in green energy storage materials. Moreover these redox behavior of these transition metal ion also leads to antimicrobial behavior in BFO.

Biography:

Dr. Sujit Kumar Bandyopadhyay is an Emeritus Fellow who served at the Meghnad Saha Institute of Technology from 2017 to 2020 and at the Institute of Engineering and Management from 2020 to 2021. He is a former Head of the Material Science Studies Division and served as Scientific Officer (H)+ and Professor at the Homi Bhabha National Institute, Variable Energy Cyclotron Centre (VECC), Department of Atomic Energy, Government of India. He retired on superannuation on 30 September 2015.

Dr. Bandyopadhyay began his career in 1978 as a Scientific Officer in the Chemical Engineering Division of the Bhabha Atomic Research Centre and joined the Variable Energy Cyclotron Centre in 1982 in the same capacity. He obtained his PhD in Physics from Jadavpur University in 1998, with a thesis titled “Charged Particle Irradiation Studies on Copper Oxide Superconductors.” In 2000, he worked as a Postdoctoral Fellow at the Atomic Institute of Austrian Universities, Vienna, focusing on magnetisation studies of neutron-irradiated high-temperature superconductor single crystals. He has been a Professor at the Homi Bhabha National Institute, a deemed university, since 2009. His achievements include the National Science Talent Search (NSTS) Scholarship and the National Scholarship from the Government of India in 1971, as well as the A. P. J. Abdul Kalam Award for outstanding research.