1,107 research outputs found
Critical properties of the double exchange ferromagnet Nd0.4Pb0.4MnO3
Results of a study of dc-magnetization M(T, H), performed on a Nd0.6Pb0.4MnO3
single crystal in the temperature range around T_C (Curie temperature) which
embraces the critical region | epsilon | = |T -T_C |/T_C <= 0.05 are reported.
The magnetic data analyzed in the critical region using the Kouvel-Fisher
method give the values for the T_C =156.47 +/- 0.06 K and the critical
exponents, beta = 0.374 +/- 0.006 (from the temperature dependence of
magnetization), and gamma = 1.329 +/- 0.003 (from the temperature dependence of
initial susceptibility). The critical isotherm M(T_C, H) gives delta = 4.547
+/- 0.1. Thus the scaling law gamma+beta=delta beta is fulfilled. The critical
exponents obey the single scaling-equation of state M(H, epsilon) = epsilon^b
f_+/- (H/epsilon^(beta + gamma)) where, f_+ for T > T_C and f_- for T< T_C. The
exponent values are very close to those expected for the universality class of
3D Heisenberg ferromagnets with short-range interactions.Comment: 19 pages, including 6 figure
Solitonic spin-liquid state due to the violation of the Lifshitz condition in FeTe
A combination of phenomenological analysis and M\"ossbauer spectroscopy
experiments on the tetragonal FeTe system indicates that the magnetic
ordering transition in compounds with higher Fe-excess, 0.11, is
unconventional. Experimentally, a liquid-like magnetic precursor with
quasi-static spin-order is found from significantly broadened M\"ossbauer
spectra at temperatures above the antiferromagnetic transition. The
incommensurate spin-density wave (SDW) order in FeTe is described by a
magnetic free energy that violates the weak Lifshitz condition in the Landau
theory of second-order transitions. The presence of multiple Lifshitz
invariants provides the mechanism to create multidimensional, twisted, and
modulated solitonic phases.Comment: 5 pages, 2 figure
Semimetalic antiferromagnetism in the half-Heusler compound CuMnSb
The half-Heusler compound CuMnSb, the first antiferromagnet (AFM) in the
Mn-based class of Heuslers and half-Heuslers that contains several conventional
and half metallic ferromagnets, shows a peculiar stability of its magnetic
order in high magnetic fields. Density functional based studies reveal an
unusual nature of its unstable (and therefore unseen) paramagnetic state, which
for one electron less (CuMnSn, for example) would be a zero gap semiconductor
(accidentally so) between two sets of very narrow, topologically separate bands
of Mn 3d character. The extremely flat Mn 3d bands result from the environment:
Mn has four tetrahedrally coordinated Cu atoms whose 3d states lie well below
the Fermi level, and the other four tetrahedrally coordinated sites are empty,
leaving chemically isolated Mn 3d states. The AFM phase can be pictured
heuristically as a self-doped CuMnSb compensated semimetal
with heavy mass electrons and light mass holes, with magnetic coupling
proceeding through Kondo and/or antiKondo coupling separately through the two
carrier types. The ratio of the linear specific heat coefficient and the
calculated Fermi level density of states indicates a large mass enhancement
, or larger if a correlated band structure is taken as the
reference
The hidden persuaders break into the tired brain
There is a long-lasting debate on whether subliminal advertising actually works. In this context there are some studies suggesting that subjects’ motivation is a crucial point. Karremans et al. [Karremans, J. C., Stroebe, W., & Claus, J. (2006). Beyond Vicary’s fantasies: The impact of subliminal priming and brand choice. Journal of Experimental Social Psychology, 42, 792–798] showed that subjects were influenced in their intention to drink a specific brand of soft drink by a subliminally presented brand prime, but only if they were thirsty. In the present study, we adapted their paradigm to the concept of ‘concentration’ and embedded the subliminal presentation of a brand logo into a computer game. Actual subsequent consumption of dextrose pills (of the presented or a not presented brand) was measured dependent on the level of participants’ tiredness and the subliminally presented logo. We found the same pattern as Karremans et al. (2006): only tired participants consumed more of the subliminally presented than the not presented brand. Therefore, the findings confirm that subjects are influenced by subliminally presented stimuli if these stimuli are need-related and if subjects are in the matching motivational state
Unbiased Black-Box Complexities of Jump Functions
International audienc
Soliton Squeezing in a Mach-Zehnder Fiber Interferometer
A new scheme for generating amplitude squeezed light by means of soliton
self-phase modulation is experimentally demonstrated. By injecting 180-fs
pulses into an equivalent Mach-Zehnder fiber interferometer, a maximum noise
reduction of dB is obtained ( dB when corrected for
losses). The dependence of noise reduction on the interferometer splitting
ratio and fiber length is studied in detail.Comment: 5 pages, 4 figure
Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: Molecular Dynamics Simulation
The scission kinetics of bottle-brush molecules in solution and on an
adhesive substrate is modeled by means of Molecular Dynamics simulation with
Langevin thermostat. Our macromolecules comprise a long flexible polymer
backbone with segments, consisting of breakable bonds, along with two side
chains of length , tethered to each segment of the backbone. In agreement
with recent experiments and theoretical predictions, we find that bond cleavage
is significantly enhanced on a strongly attractive substrate even though the
chemical nature of the bonds remains thereby unchanged.
We find that the mean bond life time decreases upon adsorption by
more than an order of magnitude even for brush molecules with comparatively
short side chains $N=1 \div 4$. The distribution of scission probability along
the bonds of the backbone is found to be rather sensitive regarding the
interplay between length and grafting density of side chains. The life time
declines with growing contour length as ,
and with side chain length as . The probability
distribution of fragment lengths at different times agrees well with
experimental observations. The variation of the mean length of the
fragments with elapsed time confirms the notion of the thermal degradation
process as a first order reaction.Comment: 15 pages, 7 figure
Nonclassical correlations in damped quantum solitons
Using cumulant expansion in Gaussian approximation, the internal quantum
statistics of damped soliton-like pulses in Kerr media are studied numerically,
considering both narrow and finite bandwidth spectral pulse components. It is
shown that the sub-Poissonian statistics can be enhanced, under certain
circumstances, by absorption, which damps out some destructive interferences.
Further, it is shown that both the photon-number correlation and the
correlation of the photon-number variance between different pulse components
can be highly nonclassical even for an absorbing fiber. Optimum frequency
windows are determined in order to realize strong nonclassical behavior, which
offers novel possibilities of using solitons in optical fibers as a source of
nonclassically correlated light beams.Comment: 15 pages, 11 PS figures (color
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