Faculty Publications
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Publications by NITK Faculty
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Item Diluted magnetism in Mn-doped SrZnO2 single crystals(American Institute of Physics Inc., 2013) Rahman, M.R.; Koteswararao, B.; Huang, S.H.; Kim, K.; Chou, F.C.We have investigated the magnetic properties of Mn- and Cu-substituted SrZnO2 single crystals (SrZn1-xMnxO2 and SrZn1-xCuxO2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the low-percentage (x = 0.01) of Mn-substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab-plane yield anisotropic behavior with Curie-Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn at high temperatures, similar to the Mn-doped ZnO and Fe-doped BaTiO3. In contrast, the SrZn0.99Cu0.01O 2 crystal shows paramagnetic behavior down to 2 K. © 2013 AIP Publishing LLC.Item Ferromagnetism in Mn-Doped ZnO: A Joint Theoretical and Experimental Study(American Chemical Society, 2021) Ali, N.; Singh, B.; A R, V.; Lal, S.; Yadav, C.S.; Tarafder, K.; Ghosh, S.We present a joint theoretical and experimental investigation on the origin of ferromagnetism in Mn-doped ZnO. Theoretical calculations revealed that the zinc vacancy (VZn) induces ferromagnetic ordering (FMO), whereas the oxygen vacancy (VO) quenches FMO in the Mn-doped ZnO system. This is further corroborated by the experimental results. Magnetic measurements revealed that Mn-doped ZnO shows room-temperature ferromagnetism (RTFM). Saturated magnetic moment per Mn2+ ion increases with oxygen partial pressure, indicating that the VZn enhances FMO in Mn-doped ZnO. Electron paramagnetic resonance and photoluminescence measurements revealed the presence of VZn in Mn-doped ZnO films. X-ray photoelectron spectroscopy measurements showed mixed oxidation states of Mn in Mn-doped ZnO films. Finally, we show that RTFM at very low doping concentrations is due to the overlapping of bound magnetic polarons. However, due to antiferromagnetic coupling at higher doping concentrations, the FMO weakens. © 2021 American Chemical Society.Item Understanding and tuning of spinterface for chemisorbed Ni-dinuclear quinonoid on Co(001) substrate(IOP Publishing Ltd, 2021) Reddy, I.R.; Tarafder, K.Planar magnetic molecules are of great research interest in the past few years because of their possible application in molecular spintronics. Microscopic understanding of the adsorption and magnetic exchange interaction of these molecules to the metallic/magnetic surfaces may pave the way in developing efficient molecular spin switching devices. Herein, using density functional theory + U calculations, we have studied the structural, electronic, and magnetic properties of a Ni-dinuclear molecule chemically adsorbed on a Co(001) substrate. Switching of the spin and oxidation state of the Ni atom present in the molecule was observed due to the adsorption. We report a strong antiferromagnetic coupling between the spins of the Ni-dinuclear molecule to the ferromagnetic Co(001) substrate. The study reveals an indirect exchange interaction between the magnetic center of the molecule and the substrate Co atoms. The exchange interaction is mediated through the ligands of the molecule that stabilizes the spin moment of the molecule in an antiferromagnetic alignment to the substrate magnetization. Our study also shows that the spin state and strength of MAE of the adsorbed molecule can be tailored through the magneto-chemical method by adding the Cl atom as an axial ligand to the magnetic center of the molecule. © 2021 IOP Publishing Ltd.