210 research outputs found
Lattice specific heat for the RMIn (R = Gd, La, Y, M = Co, Rh) compounds: non-magnetic contribution subtraction
We analyze theoretically a common experimental process used to obtain the
magnetic contribution to the specific heat of a given magnetic material. In the
procedure, the specific heat of a non-magnetic analog is measured and used to
subtract the non-magnetic contributions, which are generally dominated by the
lattice degrees of freedom in a wide range of temperatures. We calculate the
lattice contribution to the specific heat for the magnetic compounds GdMIn
(M = Co, Rh) and for the non-magnetic YMIn and LaMIn (M = Co, Rh),
using density functional theory based methods. We find that the best
non-magnetic analog for the subtraction depends on the magnetic material and on
the range of temperatures. While the phonon specific heat contribution of
YRhIn is an excellent approximation to the one of GdCoIn in the full
temperature range, for GdRhIn we find a better agreement with LaCoIn,
in both cases, as a result of an optimum compensation effect between masses and
volumes. We present measurements of the specific heat of the compounds
GdMIn (M = Co, Rh) up to room temperature where it surpasses the value
expected from the Dulong-Petit law. We obtain a good agreement between theory
and experiment when we include anharmonic effects in the calculations
Coleção de culturas de microrganismos multifuncionais da embrapa clima temperado: implementação de boas práticas.
Residual dos herbicidas imazapir e imazapique em solo, água e sedimento de lavoura de arroz irrigado no Rio Grande do Sul.
Qualidade físico-química da água de irrigação de lavoura de arroz influenciada pelo inseticida carbofurano.
Seleção de bactérias Endofíticas diazotróficas para a fixação de nitrogênio na cultivar de arroz irrigado BRS Pampa.
Persistência do herbicida nicossulfurom em Planossolo Háplico Eutrófico típico cultivado com milho.
Strongly anisotropic spin dynamics in magnetic topological insulators
The recent discovery of magnetic topological insulators has opened new
avenues to explore exotic states of matter that can emerge from the interplay
between topological electronic states and magnetic degrees of freedom, be it
ordered or strongly fluctuating. Motivated by the effects that the dynamics of
the magnetic moments can have on the topological surface states, we investigate
the magnetic fluctuations across the
(MnBiTe)(BiTe)
family. Our paramagnetic electron spin resonance experiments reveal contrasting
Mn spin dynamics in different compounds, which manifests in a strongly
anisotropic Mn spin relaxation in MnBiTe while being
almost isotropic in MnBiTe. Our density-functional
calculations explain these striking observations in terms of the sensitivity of
the local electronic structure to the Mn spin-orientation, and indicate that
the anisotropy of the magnetic fluctuations can be controlled by the carrier
density, which may directly affect the electronic topological surface states
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