Joydipto Bhattacharya

Thesis Title:
First Principles Studies on Electronic, Magnetic, and Spin Transport Properties of Bulk and Heterostructures of Heusler Alloys.

Thesis Supervisor:
Prof. Aparna Chakrabarti.

Synopsis of Thesis Work:
In the initial stages of my research, I investigated the electronic and magnetic properties of newly anticipated Full Heusler Alloy (FHA) systems of the A2BC type. Specifically, I examined Al-substituted Ga2MnNi and chalcogenide-based FHA Fe2CrTe. In the Fe2CrTe system, our focus was on the potential coexistence of half-metallicity and a tetragonal (martensitic) transition.

A combined study using Density Functional Theory (DFT) and experimental data addressed controversies over the low temperature martensite phase structure of Ni2MnGa. The existence of a charge density wave (CDW) state in the martensite phase was established, settling disagreements in the literature and confirming the CDW phase's pseudogap characteristics.

In subsequent research, magnetic interactions of various 3d transition metal (TM) adatoms on magnetic Heusler alloy surfaces (Ni2MnGa and Mn2NiGa) were investigated. Early 3d TM atoms exhibited anti-ferromagnetic coupling, while late TM atoms displayed ferromagnetic coupling. Cr and Mn demonstrated magnetic coupling dependent on surface termination and adlayer thickness.

Continuing the thesis work, the focus shifted to investigating the ballistic spin-transport characteristics of magnetic tunneling junctions (MTJs) based on Heusler alloys. Initially, electronic and spin-transport attributes of magnetic heterojunctions were examined using half-metallic and nearly half-metallic Heusler alloys as electrodes and semiconductors like MgO, NaCl, and AlN as spacers. Alternative material combinations using all-Heusler-based MTJs were explored, revealing superior interface quality, significantly higher tunnel magnetoresistance (TMR), enhanced magnetic anisotropy, and remarkably low resistance-area (RA) product compared to MgO-based MTJs.

A comprehensive analysis of magneto-crystalline anisotropy (MCA) within these magnetic heterojunctions was conducted, emphasizing its critical role in achieving high thermal stability within these structures. This research contributes valuable insights to the advancement of nanoscale spintronic devices.

• Qualified CSIR-NET 2019 (National eligibility test for lectureship)
• Qualified GATE 2019 (Graduate Aptitude Test in Engineering)
• Qualified JEST-Physics 2018 (Joint Entrance Screening Test for Ph.D. fellowship)
• Qualified IIT-JAM-Physics 2016 (Test conducted by IIT's and IISc for seeking admission in Master Program)
• Qualified JEST-Physics 2016 (Test conducted for seeking admission in Int. PhD Program)
• Ranked 5th in B. Sc. Examination conducted by University of Calcutta
• Kalikinkar Sarkar Memo. Prize for securing highest marks in Physics (Hons.) in college
• Recipient of INSPIRE scholarship for higher education, from the Department of Science & Technology (DST), Govt. of India
• Selected for short-term student exchange programme at Michigan Technological University, USA

• Physics of bulk and two-dimensional (2D) surface structures of bulk alloys
• Electronic, magnetic properties of bulk and adatoms on alloy surfaces
• Spin-transport properties of magnetic heterojunctions for spintronics applications
• Charge density wave (CDW) driven modulated structure in quasi 2D and 3D systems
• Magneto Crystalline Anisotropy in magnetic heterostructures
• Inversion symmetry breaking phenomena in semiconducting heterostructures
• 2D VdW materials for as an efficient anode material with Alkali ion storage capacity
• Symmetry protected topological states in quasi 2D VdW systems
• Transition metal-doped layered oxide cathode material
• Electronic structure under extreme conditions

• Influence of interface and external electric field on the magneto crystalline anisotropy of magnetic hetero junctions.
• Instrumental role of hybridization and bond strength in band inversion of ScIrZ(Se,Te) .
• Kramers nodal line (KNL) states in the CDW phase of YTe3.

• Presented Poster titled "Collinear Magnetic Coupling of 3d Transition Metal Atoms on Ni2MnGa (001) Surface", J. Bhattacharya and A. Chakrabarti, 65th DAE SSPS, 2021, BARC, Mumbai (Online)
• Presented Poster titled "Probing Collinear and Non-collinear Magnetic Configurations of 3d Transition metal Adlayers supported on Mn-Ga Terminated Ni2MnGa (001) Surface", J. Bhattacharya and A. Chakrabarti, Presented (Online)in APS March Meeting, USA, 2022 (Online)
• Presented Poster titled "In Search of an alternative to MgO as a spacer layer in a Heusler alloy based Magnetic Tunneling Junction : A DFT study", J. Bhattacharya and A. Chakrabarti, 11th International Conference on Fine Particles Magnetism, Japan 2022
• Presented Poster titled "Spin Polarized Transport Properties of Heusler alloy Based Magnetic Tunneling Junctions: An Ab-initio Study", J. Bhattacharya and A. Chakrabarti, IUMRS-ICA-2022, IIT Jodhpur
• Presented poster titled "Unusual magnetic and electronic properties of Al-substituted Ga2MnNi: An ab initio study" in EESTER- 2020 held during 14-18 Dec, organized by IIT Madras and SRM Jointly (Online)
• Presented poster titled "Spin Dependent Tunneling of All Heusler alloy Magnetic Tunneling Junction", ICTP Wannier 2022 Summer School (Online)

• Date of Birth: 11/07/95
• Gender: Male
• Nationality: Indian

• Ab-initio predictions of mechanical, electronic, magnetic, and transport properties of bulk and heterostructure of a novel Fe-Cr based full Heusler chalcogenide, J. Bhattacharya, R. Dutt, A. Chakrabarti, J. Phys. Chem. Solids, 178, 111307, 2023
• Charge density wave induced nodal lines in LaTe3, S. Sarkar, J. Bhattacharya, et.al, Nat. Commun, 14, 3628, 2023
• Bulk electronic structure of Ni2MnGa studied by density functional theory and hard x-ray photoelectron spectroscopy, J. Bhattacharya, P. Sadhukhan et.al, Phys. Rev. B., 108, L121114, 2023
• Electronic and transport properties of heusler alloy based magnetic tunneling junctions: A first principles study, J. Bhattacharya, A. Chakrabarti, Comput. Mater. Sci., 216, 111852, 2022
• Investigation of mechanical, lattice dynamical, electronic and thermoelectric properties of half heusler chalcogenides: a DFT study, R. Dutt, J. Bhattacharya, A. Chakrabarti, J. Phys. Chem. Solids., 167, 110704, 2022
• Surface termination and thickness dependent magnetic coupling of Cr adlayers on Ni2MnGa (001) surfaces: An ab initio study, J. Bhattacharya, et.al, J. Magn. Magn. Mater., 540, 168398, 2021
• Signature of linear-in- Dresselhaus splitting in the spin relaxation of -valley electrons in indirect bandgap AlGaAs, P. Mudi, S. K. Khamari, J. Bhattacharya, et.al, Phys. Rev. B, 104, 115202, 2021
• Study of adsorption of H2, CO and NO gas molecules on molybdenum sulfide and tungsten sulfide monolayers from first-principles calculations, D. Pandey, R. Gangwar, J. Bhattacharya, A. Chakrabarti, Surf. Sci., 714, 121910, 2021
• Unusual magnetic and electronic properties of Al-substituted Ga2MnNi: An ab initio study, A. Chakrabarti, J. Bhattacharya, et.al, J. Magn. Magn. Mater., 490, 165521, 2019
• Collinear Magnetic Coupling of 3d Transition Metal Atoms on Ni2MnGa (001) Surface, J. Bhattacharya, A. Chakrabarti, DAE SSPS (2020)
• Probing Collinear and Non-Collinear Magnetic Configurations of 3d Transition Metal Adlayers Supported on Mn-Ga Terminated Ni2MnGa (001) Surface, J. Bhattacharya, A. Chakrabarti, APS March Meeting Abstracts 2022, T00. 191
• Coherent Tunneling and Strain Sensitivity of All Heusler Alloy Magnetic Tunneling Junction A First Principles Study, J. Bhattacharya, A. Rawat, R. Pati, A. Chakrabarti, R. Pandey, https://arxiv.org/abs/2309.09755
• Bilayer stanene on a magnetic topological insulator, S. Barman, P. Bhakuni, S. Sarkar, J. Bhattacharya, et.al, https://arxiv.org/abs/2310.08265

• Dr. Aparna Chakrabarti.

      Professor, Homi Bhabha National Institute and Scientific Officer-H.

      Raja Ramanna Centre for Advanced Technology, Indore, India.

      aparnachakrabarti@gmail.com/aparna@rrcat.gov.in

• Dr. Sudipta Roy Barman.

      Professor, Devi Ahilya Devi University and Scientist H.

      UGC-DAE Consortium for Scientific Research, Khandwa Road, 

       Indore, India.

      barmansr@gmail.com

• Dr. Ranjit Pati.

      Graduate Director of Physics, Professor, Physics.

      Michigan Technological University, Houghton, USA.

      patir@mtu.edu

• Dr. Ravindra Pandey.

      Department Chair, Professor, Physics.

      Michigan Technological University, Houghton, USA.

      pandey@mtu.edu