Anamitra Mukherjee

Theory of half-metallic ferrimagnetism in double perovskites.

Double perovskites such as Sr(2)FeMoO(6) are rare examples of materials with half-metallic ground states and a ferrimagnetic T(c) above room temperature. We present a comprehensive theory of the temperature and disorder dependence of their magnetic properties by deriving and validating a new effective spin Hamiltonian for these materials, amenable to large-scale three-dimensional simulations. We show how disorder, ubiquitous in these materials, affects T(c), the magnetization, and the conduction electron polarization. We conclude with a novel proposal to enhance T(c) without sacrificing polarization.

Theory of Strain-Controlled Magnetotransport and Stabilization of the Ferromagnetic Insulating Phase in Manganite Thin Films

We show that applying strain on half-doped manganites makes it possible to tune the system to the proximity of a metal-insulator transition and thereby generate a colossal magnetoresistance (CMR) response. This phase competition not only allows control of CMR in ferromagnetic metallic manganites but can be used to generate CMR response in otherwise robust insulators at half-doping. Further, from our realistic microscopic model of strain and magnetotransport calculations within the Kubo formalism, we demonstrate a striking result of strain engineering that, under tensile strain, a ferromagnetic charge-ordered insulator, previously inaccessible to experiments, becomes stable.

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.

Conductance switching and inhomogeneous field melting in the charge ordered manganites

The field-induced switching of conductance in the charge ordered half-doped manganites is controlled by the combination of metastability, an inhomogeneous high-field state, and cation disorder. We study this non-equilibrium problem via real space Monte Carlo on a disordered strong coupling model appropriate to the manganites. We reproduce the variation of the switching fields with the mean ionic radius rA and cation disorder σA, and demonstrate how the experimental features arise from the proximity of several phases in the Landau free-energy landscape. Our prediction for the field melted state is consistent with a growing body of experimental evidence.

Adiabatic charge pumping through a dot at the junction of N quantum wires

We study adiabatic charge pumping through a quantum dot placed at the junction of

Orbital selective directional conductor in the two-orbital Hubbard model

N

Variational approach for calculating Auger electron spectra: Going beyond the impurity approximation

quantum wires. We explicitly map out the pattern of pumped charge as a function of the time-varying tunneling parameters coupling the wires to the dot and the phase between any two time-varying parameters controlling the shape of the dot. We find that with

Theory of half-metallic double perovskites. II. Effective spin Hamiltonian and disorder effects

N\ensuremath{-}2

Theory of half-metallic double perovskites. I. Double exchange mechanism

time-independent well-coupled leads, the maximum pumped charge in the remaining two leads is strongly suppressed with increasing

Exploiting B-site disorder for phase control in the manganites

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