Jyoti Thakur

Structure stability and magnetism in graphene impurity complexes with embedded V and Nb atoms

Abstract The appearance of vacancy defects could produce appropriate magnetic moment in graphene and the sensitivity to absorb atoms/molecules also increases with this. In this direction, a DFT study of embedding V and Nb atom in graphene containing monovacancies (MV) and divacancies (DV) is reported. Complete/almost complete spin polarization is detected for V/Nb embedding. The origin of magnetism has been identified via interaction of 3d -states of embedded atom with C- p states present in the vicinity of embedded site. The band structures have been analyzed to counter the observed semiconducting nature of graphene in minority spin on embedding V/Nb atom. The isosurface analysis also confirms the induced magnetism of present nanosystems. The present results reveal that these nanosystems have the potential for futuristic applications like spintronics and energy resources.

mBJLDA approach for optical properties of Nowontny-Juza LiMgZ (Z = P, As) compounds

First principles approach has been utilized to investigate electronic and optical properties of LiMgZ (Z = P, As) Newontny-Juza compounds. The exchange and correlation (XC) effects are taken into account by a semi local, orbital independent modified Becke-Johnson (mBJ) potential as coupled with Local Density Approximation (LDA). The local orbital independent mBJ potential could provide better band gap/ HM gap due to its capability to catch the essentials of hybrid functionals. The positive values of real dielectric-function rule out the possibility of showing magnetism by these compounds and stabilize the semiconducting state. The shifting of peaks in optical spectra towards high energy is due to increasing indirect band gap from LiMgP to LiMgAs.

Observation of high magnetocrystalline anisotropy on Co doping in rare earth free Fe2P magnetic material

ab-initio investigation of magnetocrystalline anisotropy energy (MAE) for Fe2P and CoFeP using density functional theory based full-potential linear augmented plane wave (FPLAPW) is reported. CoFeP alloy exhibits large magnetic moment 13.28 µB and enhanced anisotropy energy reaching as high as 1326 µeV/f.u. This energy is nearly doubled as compared to its parent Fe2P alloy, making this system a promising candidate for a rare earth free permanent magnet. Substituitng Co at Fe-3f site in Fe2P helps in stabilizing the new structure and further improves the magnetic properties.ab-initio investigation of magnetocrystalline anisotropy energy (MAE) for Fe2P and CoFeP using density functional theory based full-potential linear augmented plane wave (FPLAPW) is reported. CoFeP alloy exhibits large magnetic moment 13.28 µB and enhanced anisotropy energy reaching as high as 1326 µeV/f.u. This energy is nearly doubled as compared to its parent Fe2P alloy, making this system a promising candidate for a rare earth free permanent magnet. Substituitng Co at Fe-3f site in Fe2P helps in stabilizing the new structure and further improves the magnetic properties.

Half-Metallic ferromagnetism in V-doped ALP: An imperative compound for spintronics

A supercell approach has been used to performed the ground state calculations of Al1-xVxP (x=0.03) Diluted Magnetic Semiconductor (DMS) compound using full potential linearzed augmented plane wave (FPLAPW) method based on density functional theory (DFT). The calculated properties of bulk InP compound get modified significantly due to the substitution of V-dopant at the cation (Al) site. The new states are produced at EF which accounts for the magnetism on the doping. In V-doped AlP, the hybridization of P-p states with V-d states introduces a gap in minority spin channel with 100% spin polarization at EF. The V-doping in AlP induces a net magnetic moment of ∼2.0 μB which shows an important role played by V-d states in total magnetic moment. The HMF characteristics of V-doped AlP makes it an ideal material for spintronic devices.

A first principles study of half-metallic ferromagnetism in In1-xTixP (x = 0.06) diluted magnetic semiconductor

A first principles approach has been used to calculate the electronic and magnetic properties of In1-xTixP (x = 0.06) diluted magnetic semiconductor (DMS) compound. The calculations have been carried out using the highly precise all electron full potential Linear Augmented Plane Wave (FPLAPW) method within generalized gradient approximation (GGA) as exchange-correlation (XC) potentials. The estimated results show that the Ti-doping generate robust half metallic ferromagnetism with the 100% spin polarization at Fermi level (EF) in InP. Due to this peculiar property, the resultant compound behaves as true half-metallic ferromagnet which is best suited for spintronic applications. The total magnetic moments of this compound are mainly due to Ti-d states present at EF with almost negligible contribution from other atoms.

Electronic and magnetic properties of Mo doped graphene; full potential approach

The electronic and magnetic properties of pristine and Cr doped graphene have been calculated using WIEN2k implementation of full potential linearized augmented plane wave (FPLAPW) method based on Density Functional Theory (DFT). The exchange and correlation (XC) effects were taken into account by generalized gradient approximation (GGA). The calculated results show that Cr doping introduces appropriate magnetic moment on graphene. The p-d interaction between 3d states of Cr atom and p-states of C atom are responsible for half metallicity in graphene. The calculated Half-metallic behavior of Cr-doped graphene makes it an ideal candidate for spintronic applications.

Enhancement of spin polarization via Fermi level tuning in Co2MnSn1−xSbx (x = 0, 0.25. 0.5, 0.75, 1) Heusler alloys

Full potential approach has been employed to tune Fermi level in Co2MnSn1−xSbx (x = 0, 0.25, 0.5, 0.75, 1) Heulser alloys for enhancement of spin polarization and finding signature of half metallicity. Present density functional theory (DFT) based calculation indicates that stoichoimetric Heusler alloy, Co2MnSn is not a half-metallic ferromagnet but the doping of Sb in it results in the shifting of EF in well-defined energy gap which leads the 100% spin polarization in the resultant alloys. The magnetism in present alloys is governed by localized moment on Mn atom mainly. The tuning of half-metallicity using doping can be proved as an ideal technique to search the new materials which can accomplish the need of spintronics.

Half-metallic ferromagnetism in Cr-doped semiconducting Ge-chalcogenide: Density functional approach

A supercell approach has been used to calculate the electronic and magnetic properties of Cr-doped Ge chalcogenide, Ge1−xCrxTe (x = 0.25 and 0.125). The calculations have been performed using full potential Linear Augmented Plane Wave (FPLAPW) method within generalized gradient approximation (GGA) as exchange-correlation (XC) potential. The calculated results show that the doping of Cr induces the 100% spin polarization at Fermi level (EF) and showed the robust half metallic ferromagnetism in this compound. Thus, the compound at both dopant concentrations behave as dilute magnetic semiconductor (DMS) showing metallic property in majority and semiconducting for minority spin channels which is best suited for spintronic applications. The total magnetic moments of this compound are mainly due to Cr-d states present at EF with negligible contribution from electronic states of other atoms.