865 research outputs found
Magnetic field splitting of the spin-resonance in CeCoIn5
Neutron scattering in strong magnetic fields is used to show the
spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The
underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two
modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A
linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T,
near the critical field for the incommensurate "Q-phase" indicating that the
Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure
Fifth Graders’ Creativity in Inventions with and without Creative Articulation Instruction
Industry and authors of 21st Century Skill Frameworks are calling for student proficiency in creativity, problem-solving, innovation, collaboration, and communication skills. This project involved 13 fifth grade gifted students in inventing products for a specified audience with a set of given materials, time limit, and topic constraints. The complex, challenging project supports Next Generation Science Engineering Process Standard 3-5-ETS1-2 and applies concepts of plant and animal adaptations. The study had a counterbalanced, repeated measures design in which student made an initial invention during the pretest, then participated in two trials with one in the control condition and the other in the experimental condition. The experimental condition involved creative articulation strategies of considering the audience for the invention, effective communication of the ways the product meets audience needs, and peer collaboration and feedback to improve the product ideas. Students found the invention process initially very challenging, especially generating unique ideas. No statistically significant differences were found in product creativity or student attitudes, which were very positive, between the two conditions of the experiment, likely because of the small sample size. Analysis of student advertisements revealed a statistically significant difference favoring the experimental condition with a medium effect size for including reasons the product meets audience needs in the advertisement. Examples of student-made products and teacher analysis of selected products provide ideas for coaching students into higher creative skill levels. Additionally, statistically significant gains in creativity skill occurred from the pretest to the invention of the product during the first trial and this was maintained into the second trial with large effect size. This study showed that multiple invention opportunities allowed students to develop their skills better than a single activity. The challenging, complex activities helped students achieve a state of flow as they worked during the experiment and helped students develop their creativity
Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3V2O8 in a transverse magnetic field
The application of a magnetic field transverse to the easy axis, Ising
direction in the quasi-two-dimensional Kagome staircase magnet, Co3V2O8,
induces three quantum phase transitions at low temperatures, ultimately
producing a novel high field polarized state, with two distinct sublattices.
New time-of-flight neutron scattering techniques, accompanied by large angular
access, high magnetic field infrastructure allow the mapping of a sequence of
ferromagnetic and incommensurate phases and their accompanying spin
excitations. At least one of the transitions to incommensurate phases at \mu
0Hc1~6.25 T and \mu 0Hc2~7 T is discontinuous, while the final quantum critical
point at \mu 0Hc3~13 T is continuous.Comment: 5 pages manuscript, 3 pages supplemental materia
Commensurate Fluctuations in the Pseudogap and Incommensurate spin-Peierls Phases of TiOCl
X-ray scattering measurements on single crystals of TiOCl reveal the presence
of commensurate dimerization peaks within both the incommensurate spin-Peierls
phase and the so-called pseudogap phase above T_c2. This scattering is
relatively narrow in Q-space indicating long correlation lengths exceeding ~
100 A below T* ~ 130 K. It is also slightly shifted in Q relative to that of
the commensurate long range ordered state at the lowest temperatures, and it
coexists with the incommensurate Bragg peaks below T_c2. The integrated
scattering over both commensurate and incommensurate positions evolves
continuously with decreasing temperature for all temperatures below T* ~ 130 K.Comment: To appear in Physical Review B: Rapid Communications. 5 page
Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor
The upgrade of the cold neutron triple-axis spectrometer FLEXX is described.
We discuss the characterisation of the gains from the new primary spectrometer,
including a larger guide and double focussing monochromator, and present
measurements of the energy and momentum resolution and of the neutron flux of
the instrument. We found an order of magnitude gain in intensity (at the cost
of coarser momentum resolution), and that the incoherent elastic energy widths
are measurably narrower than before the upgrade. The much improved count rate
should allow the use of smaller single crystals samples and thus enable the
upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table
Social Studies Content Reading about the American Revolution Enhanced with Graphic Novels
Graphic novels can contribute to effective content area reading on social studies topics such as the American Revolution. This action research study’s purpose was to examine student recall of facts, enjoyment of reading, and interest in the topic when using graphic novels as compared to illustrated nonfiction prose in social studies content area reading. Twenty-two fifth grade students (13 females, 9 males) in a public school in a Midwestern state participated in the study. Half of the students read about the Boston Massacre and Patrick Henry through graphic novels and read about Paul Revere and the Boston Tea Party with illustrated nonfiction texts, with the other half doing the opposite. The mean number of correct ideas recalled by students two weeks after reading two books in the graphic novel condition was 8.6 compared to 7.1 for the nonfiction prose condition with a medium effect size. Students rated their reading enjoyment significantly higher in the graphic novel condition indicating that graphic novels should be employed more often into the school curriculum. Suggestions for integrating graphic novels into the curriculum are provided along with other ways to take action
Suppression of the commensurate spin-Peierls state in Sc-doped TiOCl
We have performed x-ray scattering measurements on single crystals of the
doped spin-Peierls compound Ti(1-x)Sc(x)OCl (x = 0, 0.01, 0.03). These
measurements reveal that the presence of non-magnetic dopants has a profound
effect on the unconventional spin-Peierls behavior of this system, even at
concentrations as low as 1%. Sc-doping suppresses commensurate fluctuations in
the pseudogap and incommensurate spin-Peierls phases of TiOCl, and prevents the
formation of a long-range ordered spin-Peierls state. Broad incommensurate
scattering develops in the doped compounds near Tc2 ~ 93 K, and persists down
to base temperature (~ 7 K) with no evidence of a lock-in transition. The width
of the incommensurate dimerization peaks indicates short correlation lengths on
the order of ~ 12 angstroms below Tc2. The intensity of the incommensurate
scattering is significantly reduced at higher Sc concentrations, indicating
that the size of the associated lattice displacement decreases rapidly as a
function of doping.Comment: 7 pages, 5 figure
Instability of Magnons in Two-dimensional Antiferromagnet at High Magnetic Fields
Spin dynamics of the square lattice Heisenberg antiferromagnet, \BaMnGeO, is
studied by a combination of bulk measurements, neutron diffraction, and
inelastic neutron scattering techniques. Easy plane type antiferromagnetic
order is identified at K. The exchange interactions are estimated
as = 27.8(3)eV and = 1.0(1) eV, and the saturation
field is 9.75 T. Magnetic excitation measurements with high
experimental resolution setup by triple axis neutron spectrometer reveals the
instability of one magnon excitation in the field range of .Comment: 5 pgase, 5 figuers, to be published in PRB R
Luttinger-Liquid Behavior in the Alternating Spin-Chain System Copper Nitrate
We determine the phase diagram of copper nitrate Cu(NO)2.5DO
in the context of quantum phase transitions and novel states of matter. We
establish this compound as an ideal candidate to study quasi-1D Luttinger
liquids, 3D Bose-Einstein-Condensation of triplons, and the crossover between
1D and 3D physics. Magnetocaloric effect, magnetization, and neutron scattering
data provide clear evidence for transitions into a Luttinger liquid regime and
a 3D long-range ordered phase as function of field and temperature. Theoretical
simulations of this model material allow us to fully establish the phase
diagram and to discuss it in the context of dimerized spin systems.Comment: 5 pages, 4 figure
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