Hardev S. Saini

Effect of substituting sp-element on half metallic ferromagnetism in NiCrSi Heusler alloy

We present a first principle study of new class of high-Tc half-heusler ferromagnets NiCrZ (Z = Si, P, Ge, As, Te). The structure and magnetic properties are investigated through the calculation of the electronic structure, equilibrium lattice constant, magnetic exchange interaction Jij and Curie temperature Tc. The role of sp-elements and the influence of lattice expansion/compression are also studied. In alloys having 20 valence electrons, a pseudo-gap of the majority band can be formed at Fermi level. Otherwise, the half-metallicity and ferromagnetism at temperatures much higher than room temperature are found to be stable in a wide range of lattice expansion. Based on these results, NiCrZ can be expected to be promising materials for spintronics. ∗Electronic address: divan@cmp.sanken.osaka-u.ac.jp.

Effect of oxygen vacancy on half metallicity in Ni-doped CeO2 diluted magnetic semiconductor

The electronic and magnetic properties of Ni-doped CeO2 diluted amgentic semiconductor (DMS) including the effect of oxygen vacancy (Vo) with doping concentration, x = 0.125 have been calculated using FPLAPW method based on Density Functional Theory (DFT) as implemented in WIEN2k. In the present supercell approach, the XC potential was constructed using GGA+U formalism in which Coulomb correction is applied to standard GGA functional within the parameterization of Perdew-Burke-Ernzerhof (PBE). We have found that the ground state properties of bulk CeO2 compound have been modified significantly due to the substitution of Ni-dopant at the cation (Ce) site with/without VO and realized that the ferromagnetism in CeO2 remarkably depends on the Vo concentrations. The presence of Vo, in Ni-doped CeO2, can leads to strong ferromagnetic coupling between the nearest neighboring Ni-ions and induces a HMF in this compound. Such ferromagnetic exchange coupling is mainly attributed to spin splitting of Ni-d states, via...

Investigation of half-metallic ferromagnetism in Ti-doped BeS DMS compound: A promising spintronic material

The first principles calculationshave been performed to calculate the electronic and magnetic properties of Be1-xTixS (x=0.03 and 0.06) Diluted Magnetic Semiconductor (DMS) compound using full potential linearized augmented plane wave (FPLAPW) method based on density functional theory (DFT). The estimatedresults show that the substitution of Ti-dopant at the cation (Be) site alters the ground state properties of host BeS compound significantly and the resultant compounds becomes true half metallic (HM) ferromagnet. This behavior is due to the hybridization of S-p states with Ti-d states at/near EF which introduces a gap in minority spin channel with 100% spin polarization at EF. The resultant compounds at both dopant concentrations have band gap at the Fermi level (EF) for only one spin channel and showing metallic property for other spin channel which is desired feeeature for spintronic applications. The Ti-doping in BeS induces a net magnetic moment of∼2.0 µB which shows an important role played by Ti-d states in total magnetic moment. The half metallic character of Ti-doped BeS makes it as promising material for spintronic devices.The first principles calculationshave been performed to calculate the electronic and magnetic properties of Be1-xTixS (x=0.03 and 0.06) Diluted Magnetic Semiconductor (DMS) compound using full potential linearized augmented plane wave (FPLAPW) method based on density functional theory (DFT). The estimatedresults show that the substitution of Ti-dopant at the cation (Be) site alters the ground state properties of host BeS compound significantly and the resultant compounds becomes true half metallic (HM) ferromagnet. This behavior is due to the hybridization of S-p states with Ti-d states at/near EF which introduces a gap in minority spin channel with 100% spin polarization at EF. The resultant compounds at both dopant concentrations have band gap at the Fermi level (EF) for only one spin channel and showing metallic property for other spin channel which is desired feeeature for spintronic applications. The Ti-doping in BeS induces a net magnetic moment of∼2.0 µB which shows an important role played by Ti-d...

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.

Stability of high spin polarization via substituting spelement in Co2MnSn1−xGax Heusler alloys

The stability of high spin polarization in Co2MnSn1−xGax (x = 0, 0.25, 0.5, 0.75, 1) Heulser alloys via substitution of sp-element has been studied using Full potential linearized augmented plane wave (FPLAPW) method. We demonstrate that substitution of Ga for Sn maintains a high degree of spin polarization, throughout all intermediate alloys. The magnetism in present alloys is governed by localized moment on Mn atom mainly. This wide range of highly spin polarized materials can be proved as ideal candidates for magneto-electronic devices.

Tuning magnetism in semiconducting cadmium chalcogenides via Cr-doping

The electronic and magnetic properties of Cr-doped cadmium chalcogenides, Cd1-xCrxS and Cd1-xCrxSe (x = 0.125 are presented using supercell approach. 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 ferromagnetism in both compounds and the resultant compounds show robust half metallicity and 100% spin polarization at Fermi level (EF). The band gap for both compounds disappears from majority spin. Thus the compounds behave as dilute magnetic semiconductors (DMS) showing metallic property in majority and semiconducting for minority spin channels which is best suited for spintronic applications. The total magnetic moments of these compounds are mainly due to Cr-d states present at EF with negligible contribution from other atoms.

Mn-Disorder Effect on Magnetism and Half Metallicity of NiCoMnGa Quaternary Heusler Alloy

The full potential linearized augmented plane wave (FPLAPW) method within generalized gradient approximation (GGA) has been used to investigate the effect of disorder between Ni and Mn atoms on the electronic and magnetic properties of NiCoMnGa quaternary Heusler alloy. We observed that the increase in Mn concentration in NiCoMnGa destroys the half metallicity and decreases the total magnetic moment. Further, the disordered alloy exists in ferrimagnetic (FiM) ground state rather than ferromagnetic (FM) one of ordered system due to antiparallel alignment of extra Mn atom with respect to original Mn atom.