76 research outputs found
Electronic band structure and Fermi surface of AgPbO
We present electronic band structure of AgPbO with layered
hexagonal structure containing one-dimensional chains and two-dimensional
Kagom\'{e} layers of silver. A half-filled conduction band shows extremely
simple, single nearly-free-electron-like Fermi surface. The conduction band is
composed of an antibonding state of Pb- and O- mixing with Ag-4d and
. Mass enhancement in the state density at the Fermi energy is expected to
be negligibly small by comparing with the specific-heat data. Calculated Fermi
velocity is consistent with small anisotropy observed in transport properties.
Doping effects on the electronic structure are also discussed.Comment: 6 pages, 9 figures; fig7 replaced, reference 6 adde
Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2
Extremely large magnetoresistance is realized in the nonmagnetic layered
metal PdCoO2. In spite of a highly conducting metallic behavior with a simple
quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance
reaches up to 35000% for the field along the [1-10] direction. Furthermore, the
temperature dependence of the resistance becomes nonmetallic for this field
direction, while it remains metallic for fields along the [110] direction. Such
severe and anisotropic destruction of the interlayer coherence by a magnetic
field on a simple Fermi surface is ascribable to orbital motion of carriers on
the Fermi surface driven by the Lorentz force, but seems to have been largely
overlooked until now.Comment: Phys. Rev. Lett. 111, 056601 (2013
Anisotropic magnetocaloric effect of CrI: A theoretical study
CrI is considered to be a promising candidate for spintronic devices
and data storage. We derived the Heisenberg Hamiltonian for CrI from
density functional calculations using the Liechtenstein formula. Moreover, the
Monte--Carlo simulations with the Sucksmith--Thompson method were performed to
analyze the effect of magnetic anisotropy energy on the thermodynamic
properties. Our method successfully reproduced the negative sign of isothermal
magnetic entropy changes when a magnetic field was applied along the hard
plane. We found that the temperature dependence of the magnetocrystalline
anisotropy energy is not negligible at temperatures slightly above the Curie
temperature. We clarified that the origin of this phenomenon is attributed to
anisotropic magnetic susceptibility and magnetization anisotropy. The
difference between the entropy change of the easy axis and the hard plane is
proportional to the temperature dependence of the magnetic anisotropy energy,
implying that the anisotropic entropy term is the main source of the
temperature dependence of the free energy difference when magnetizing in a
specific direction other than the easy axis. We also investigated the magnetic
susceptibility that can be used for the characterization of the negative sign
of the entropy change in the case of a hard plane. The competition of
magnetocrystalline anisotropy energy and external magnetic field at low
temperature and low magnetic field region causes a high magnetic susceptibility
as the fluctuation of magnetization. Meanwhile, the anisotropy energy is
suppressed at a sufficient magnetic field applied along the hard axis, the
magnetization is fully rotated to the direction of the external magnetic field
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