18,037 research outputs found
Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes
Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black
hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the
Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as
the Ruppeiner scalar curvature and find that the singular points are not the
same with the ones obtained using the heat capacity. Legendre-invariant metric
proposed by Quevedo and the metric obtained by using the free energy as the
thermodynamic potential are obtained and the corresponding scalar curvatures
diverge at the Davies points.Comment: Latex,19 pages,14 figure
Crystal structure and physical properties of half-doped manganite nanocrystals with size < 100nm
In this paper we report the structural and property (magnetic and electrical
transport) measurements of nanocrystals of half-doped
(LCMO) synthesized by chemical route, having
particle size down to an average diameter of 15nm. It was observed that the
size reduction leads to change in crystal structure and the room temperature
structure is arrested so that the structure does not evolve on cooling unlike
bulk samples. The structural change mainly affects the orthorhombic distortion
of the lattice. By making comparison with observed crystal structure data under
hydrostatic pressure it is suggested that the change in the crystal structure
of the nanocrystals occurs due to an effective hydrostatic pressure created by
the surface pressure on size reduction. This not only changes the structure but
also causes the room temperature structure to freeze-in. The size reduction
also does not allow the long supercell modulation needed for the Charge
Ordering, characteristic of this half-doped manganite, to set-in. The magnetic
and transport measurements also show that the Charge Ordering (CO) does not
occur when the size is reduced below a critical size. Instead, the nanocrystals
show ferromagnetic ordering down to the lowest temperatures along with metallic
type conductivity. Our investigation establishes a structural basis for the
destabilization of CO state observed in half-doped manganite nanocrystals.Comment: 11 pages, 13 Figure
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