title: Colossal magnetoresistance in amino-functionalized graphene quantum dots at room temperature: manifestation of weak anti-localization and doorway to spintronics.
abstract: In this work, we have demonstrated the signatures of localized surface distortions and disorders in functionalized graphene quantum dots (fGQD) and consequences in magneto-transport under weak field regime (∼1 Tesla) at room temperature. Observed positive colossal magnetoresistance (MR) and its suppression is primarily explained by weak anti-localization phenomenon where competitive valley (inter and intra) dependent scattering takes place at room temperature under low magnetic field; analogous to low mobility disordered graphene samples. Furthermore, using ab-initio analysis we show that sub-lattice sensitive spin-polarized ground state exists in the GQD as a result of pz orbital asymmetry in GQD carbon atoms with amino functional groups. This spin polarized ground state is believed to help the weak anti-localization dependent magneto transport by generating more disorder and strain in a GQD lattice under applied magnetic field and lays the premise for future graphene quantum dot based spintronic applications.
authors.affiliation: Thin Film and Nanoscience Laboratory, Dept. of Physics, Jadavpur University, Kolkata-700032, India. kalyan_chattopadhyay@yahoo.com and School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032, India.
authors.forename: Rajarshi
authors.initials: R
authors.lastname: Roy
authors.affiliation: SRM Research Institute, SRM University, Kattankulathur-603203, Tamil Nadu, India.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Thapa
authors.affiliation: School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032, India.
authors.forename: Gundam Sandeep
authors.initials: GS
authors.lastname: Kumar
authors.affiliation: Thin Film and Nanoscience Laboratory, Dept. of Physics, Jadavpur University, Kolkata-700032, India. kalyan_chattopadhyay@yahoo.com.
authors.forename: Nilesh
authors.initials: N
authors.lastname: Mazumder
authors.affiliation: Thin Film and Nanoscience Laboratory, Dept. of Physics, Jadavpur University, Kolkata-700032, India. kalyan_chattopadhyay@yahoo.com.
authors.forename: Dipayan
authors.initials: D
authors.lastname: Sen
authors.affiliation: SRM Research Institute, SRM University, Kattankulathur-603203, Tamil Nadu, India.
authors.forename: S
authors.initials: S
authors.lastname: Sinthika
authors.affiliation: School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032, India.
authors.forename: Nirmalya S
authors.initials: NS
authors.lastname: Das
authors.affiliation: Thin Film and Nanoscience Laboratory, Dept. of Physics, Jadavpur University, Kolkata-700032, India. kalyan_chattopadhyay@yahoo.com and School of Materials Science and Nanotechnology, Jadavpur University, Kolkata-700032, India.
authors.forename: Kalyan K
authors.initials: KK
authors.lastname: Chattopadhyay