PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...
PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...
PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...
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Introduction 13<br />
Figure 1.10: A schematic picture of the antiferromagnetic pseudo-CE-type structure<br />
in the case of Pr 1−x Ca x MnO 3 (x = 0.4) [38].<br />
in Fig. 1.10, where the arrangement of spin is canted along the c-axis while the<br />
CE-type ordering is kept within the orthorhombic ab-plane. For the ground state<br />
of R 1−x A x MnO 3 , i.e AMnO 3 (x = 1), the magnetic structure is called G-type AFM<br />
[34, 39] ordering in which the spins on all Mn 4+ sites are antiparallel to their nearest<br />
neighbours.<br />
1.9 Pseudogap behavior in manganites<br />
The conducting properties of the materials depend on the finer changes associated<br />
with the density of states (DOS) near the Fermi level. If there are no allowed states<br />
at the Fermi level a gap forms by making the system insulating and finite density of<br />
states makes the system metallic. A Pseudogap exists in the mixed-phase regimes of<br />
manganites, which suggests that the prominent depletion of spectral weight (density<br />
of states) at the chemical potential, but not exactly zero (few states associated with<br />
it). This feature is similar to that extensively discussed in high T c superconductor.<br />
The calculations in the pseudogap context in manganites was carried out by Moreo<br />
et. al. [40, 41] using both one- and two-orbital models (Fig. 1.11). The density of<br />
states of the one-orbital model on 2D cluster varying the electronic density slightly<br />
below 〈n〉 = 1.0 is shown in the Fig. 1.11(a). At zero temperature, this density<br />
regime is unstable due to phase separation, but at the temperature of simulation<br />
those densities still correspond to stable states, but with a dynamical mixture of