256,647 research outputs found
Anomalous magneto-structural behavior of MnBi explained: a path towards an improved permanent magnet
Low-temperature MnBi (hexagonal NiAs phase) exhibits anomalies in the lattice
constants (a, c) and bulk elastic modulus (B) below 100 K, spin reorientation
and magnetic susceptibility maximum near 90 K, and, importantly for
high-temperature magnetic applications, an increasing coercivity (unique to
MnBi) above 180 K. We calculate the total energy and magneto-anisotropy energy
(MAE) versus (a, c) using DFT+U methods. We reproduce and explain all the above
anomalies. We predict that coercivity and MAE increase due to increasing a,
suggesting means to improve MnBi permanent magnets.Comment: 4 pages, 5 figure
Optical properties of TlNi2Se2: Observation of pseudogap formation
The quasi-two-dimensional nickel chalcogenides is a newly
discovered superconductor. We have performed optical spectroscopy study on
single crystals over a broad frequency range at various
temperatures. The overall optical reflectance spectra are similar to those
observed in its isostructure . Both the suppression in
and the peaklike feature in suggest the progressive
formation of a pseudogap feature in the midinfrared range with decreasing
temperatures, which might be originated from the dynamic local fluctuation of
charge-density-wave (CDW) instability. We propose that the CDW instability in
is driven by the saddle points mechanism, due to the existence of
van Hove singularity very close to the Fermi energy.Comment: 5 pages, 4 figure
Corrections to scaling in the dynamic approach to the phase transition with quenched disorder
With dynamic Monte Carlo simulations, we investigate the continuous phase
transition in the three-dimensional three-state random-bond Potts model. We
propose a useful technique to deal with the strong corrections to the dynamic
scaling form. The critical point, static exponents and , and
dynamic exponent are accurately determined. Particularly, the results
support that the exponent satisfies the lower bound .Comment: 10 pages, 6 figures, 2 table
Tunable near- to mid-infrared pump terahertz probe spectroscopy in reflection geometry
Strong-field mid-infrared pump--terahertz (THz) probe spectroscopy has been
proven as a powerful tool for light control of different orders in strongly
correlated materials. We report the construction of an ultrafast broadband
infrared pump--THz probe system in reflection geometry. A two-output optical
parametric amplifier is used for generating mid-infrared pulses with GaSe as
the nonlinear crystal. The setup is capable of pumping bulk materials at
wavelengths ranging from 1.2 m to 15 m and beyond, and detecting the
subtle, transient photoinduced changes in the reflected electric field of the
THz probe at different temperatures. As a demonstration, we present 15 m
pump--THz probe measurements of a bulk EuSbTe single crystal. A
transient change in the reflected THz electric field can be clearly resolved.
The widely tuned pumping energy could be used in mode-selective excitation
experiments and applied to many strongly correlated electron systems.Comment: 4 pages, 4 figure
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