arXiv subjects

G. P. Das

Publications and source records attributed to G. P. Das.

24 records · Page 2Linked to original sources

arXiv2006

Calculations of spin induced transport in ferromagnets

Based on first-principles density functional calculations, a general approach for determining and analyzing the degree of spin polarization (P) in ferromagnets is presented. The approach employs the so-called tetrahedron method to evaluate the Fermi surface integrations of P in both ballistic and diffusive regimes. The validity of the method is examined by comparing the calculated P values for Fe and Ni with the experiment. The method is shown to yield highly accurate results with minimal computational effort. Within our approach, it is also possible to systematically analyze the contributions of various types of electronic states to the spin induced transport. As a case study, the transport properties of the soft-ferromagnet CeMnNi4 are investigated in order to explain the origin of the existing difference between the experimental and theoretical values of P in this intermetallic compound.

cond-mat.mtrl-sci↗

arXiv2005

Ab-inito study on different phases of ferromagnetic CeMnNi4

Using first-principles density functional calculations, we study the possible phases of CeMnNi$_{4}$ and show that the ground state is ferromagnetic. We observed the hexagonal phase to be lowest in energy whereas experimentally observed cubic phase lies slightly higher in energy. We optimized the structure in both phases and in all different magnetic states to explore the possibility of the structural and magnetic phase transitions at ground state. We do not find any phase transitions between the magnetic and non-magnetic phases. The calculated structural, magnetic properties of cubic phase are in excellent agreement with experiments. Further, we do not observe half metallic behavior in any of the phases. However, the cubic phase does have fewer density of states for down-spin component giving a possibility of forming half metallic phase artificially, introducing vacancies, and disorder in lattice.

cond-mat.mtrl-sci↗

arXiv2002

Ferromagnetism in Cr-doped GaN: A First Principles Calculation

Otherwise antiferromagnetic chromium is shown to couple ferromagnetically when doped into GaN irrespective of whether the host is a crystal or a cluster. The results on the doped clusters and crystals are obtained from density functional theory based molecular orbital theory and linearized muffin tin orbital tight binding supercell band structure method respectively. The calculated half metallic behavior of Cr-doped GaN crystal combined with the observed room temperature Curie point make it an ideal candidate for spintronics applications.

cond-mat.mtrl-sci↗

arXiv2002

Ferromagnetism in Mn-doped GaN: From Clusters to Crystals

The magnetic coupling between doped Mn atoms in clusters as well as crystals of GaN has been studied from first principles using molecular orbital theory for clusters and linearized muffin tin orbitals-tight binding formulation (LMTO-TB) for crystals. The calculations, based on density functional theory and generalized gradient approximation for exchange and correlation, reveal the coupling to be ferromagnetic with a magnetic moment ranging from 2.0 to 4.0 Bohr magnetons per Mn atom depending on its environment. Mn atoms also tend to cluster and bind more strongly to N atoms than to Ga atoms. The significant binding of Mn to GaN clusters further indicates that it may be possible to increase the Mn concentration in GaN by using a porous substrate that offers substantial interior surface sites.

cond-mat.mtrl-sci↗

arXiv2000

Local magnetism of isolated Mo atoms at substitutional and interstitial sites in Yb metal : Experiment and Theory

Using TDPAD experiment and local spin density calculations, we have observed large 4d moments on isolated Mo atoms at substitutional and octahedral interstitial lattice sites in Yb metal, showing Curie-Weiss local susceptibility and Korringa like spin relaxation rate. As a surprising feature, despite strong hybridization with the Yb neighbours, interstitial Mo atoms show high moment stability with small Kondo temperature. While, magnetism of Mo, at substitutional site is consistent with Kondo type antiferromagnetic d-sp exchange interaction, we suggest that moment stability at the interstitial site is strongly influenced by ferromagnetic polarization of Yb-4f5d band electrons.

cond-mat↗

arXiv1999

An augmented space recursion study of the electronic structure of rough epitaxial overlayers

In this communication we propose the use of the Augmented Space Recursion as an ideal methodology for the study of electronic and magnetic structures of rough surfaces, interfaces and overlayers. The method can take into account roughness, short-ranged clustering effects, surface dilatation and interdiffusion. We illustrate our method by an application of Fe overlayer on Ag (100) surface.

cond-mat.mtrl-sci↗