Kalpataru Pradhan

Distinct effects of homogeneous weak disorder and dilute strong scatterers on phase competition in manganites.

We study the two orbital double-exchange model in two dimensions including antiferromagnetic (AFM) superexchange, Jahn-Teller coupling, and substitutional disorder. At hole doping x = 0.5 we focus on phase competition between the ferromagnetic metal (FMM) and the charge-ordered (CO) and orbital-ordered (OO) CE state and compare the impact of weak homogeneous disorder to that of a low density of strong scatterers. Even moderate homogeneous disorder suppresses the CE-CO-OO phase and leads to a glass with nanoscale correlations, while dilute strong scatterers of comparable strength convert the CE-CO-OO phase to a phase separated state with ferromagnetic metal and AFM-CO-OO clusters.

Enhanced magnetic moments of alkali metal coated Sc clusters: New magnetic superatoms

It is shown that the magnetic moments of Sc atoms can be significantly enhanced by combining them with alkali atoms. We present results of first principles electronic structure calculations of ScNa(n) (1 < or = n < or = 12) clusters that indicate that a ScNa(12) cluster consisting of a Sc atom surrounded by 12 Na atoms forming a compact icosahedral structure has a spin magnetic moment of 3 micro(B) that is three times that of an isolated Sc atom. This unusual behavior is analyzed in terms of the filling of the supershells 1S, 1P,... controlled by the nature and size of the alkali atoms and the more localized Sc 3d orbitals that hybridize weakly with Na sp orbitals. It is shown that even larger magnetic moments could be attained by controlling the relative position of 1S, 1P, and 3d states. Indeed, our studies indicate large magnetic moment five times that of an isolated Sc atom in the ScK(12) and ScCs(12) clusters, in which the 3d orbitals of Sc adopt a half-filled configuration, while the clusters are stabilized by filled 1S(2), 1P(6), and 2S(2) shells, the features making them as new magnetic superatoms.

Evolution of superhalogen properties in PtCln clusters

We have systematically calculated the ground state geometries, relative stability, electronic structure, and spectroscopic properties of PtCl(n) (n = 1-7) clusters. The bonding in these clusters is dominated by covalent interaction. In neutral clusters, chlorine atoms are chemically bound to Pt up to n = 5. However, in neutral PtCl(6) and PtCl(7) clusters, two of the chlorine atoms bind molecularly while the remaining bind as individual atoms. In the negative ions, this happens only in the case of PtCl(7) cluster. The geometries of both neutral and anionic clusters can be considered as fragments of an octahedron and are attributed to the stabilization associated with splitting of partially filled d orbitals under the chloride ligand field. The electron affinity of PtCl(n) clusters rises steadily with n, reaching a maximum value of 5.81 eV in PtCl(5). PtCl(n) clusters with n ≥ 3 are all superhalogens with electron affinities larger than that of chlorine. The accuracy of our results has been verified by carrying out photoelectron spectroscopy experiments on PtCl(n)(-) anion clusters.

First principles study of Sc, Ti, and V doped Na n ( n = 4 , 5 , 6 ) clusters: Enhanced magnetic moments

Theoretical studies on the geometry, electronic structure, and spin multiplicity of Sc, Ti, and V doped

First-principles study of TMNan (TM = Cr, Mn, Fe, Co, Ni; n = 4-7) clusters

{\mathrm{Na}}_{n}

Electronic and magnetic reconstructions in manganite superlattices

(n=4,5,6)

Conductance switching and inhomogeneous field melting in the charge ordered manganites

clusters have been carried out within a gradient corrected density functional approach. Two complementary approaches including all-electron calculations on free clusters and supercell calculations using plane-wave pseudopotential and projector augmented wave formalisms have been carried out. It is shown that spin magnetic moments of the transition metal atoms, the magnitude of host polarization, and the sign of the host polarization all change with the number of alkali atoms. In particular, the transition metal atoms are shown to attain spin moments that are higher than their atomic values. The role of hybridization between the transition atom

Interfacial magnetism in manganite superlattices

d

Nanoclustering phase competition induces the resistivity hump in colossal magnetoresistive manganites

states and the alkali