184 research outputs found
Observation of a half step magnetization in the {Cu-3}-type triangular spin ring
We report pulsed field magnetization and ESR experiments on a {Cu-3} nanomagnet, where antiferromagnetically coupled Cu2+ (S=1/2) ions form a slightly distorted triangle. The remarkable feature is the observation of a half step magnetization, hysteresis loops, and an asymmetric magnetization between a positive and a negative field in a fast sweeping external field. This is attributed to an adiabatic change of magnetization. The energy levels determined by ESR unveil that the different mixing nature of a spin chirality of a total S=1/2 Kramers doublet by virtue of Dzyaloshinskii-Moriya interactions is decisive for inducing half step magnetization.</p
Magnetic characterization of the frustrated three-leg ladder compound [(CuCl2tachH)3Cl]Cl2
We report the magnetic features of a new one-dimensional stack of
antiferromagnetically coupled equilateral copper(II) triangles. High-field
magnetization measurements show that the interaction between the copper
triangles is of the same order of magnitude as the intra-triangle exchange
although only coupled via hydrogen bonds. The infinite chain turns out to be an
interesting example of a frustrated cylindrical three-leg ladder with competing
intra- and inter-triangle interactions. We demonstrate that the ground state is
a spin singlet which is gaped from the triplet excitation.Comment: 6 pages, 9 figures, revised version submitted to Phys. Rev. B. More
information at http://obelix.physik.uni-osnabrueck.de/~schnack
A table-top, repetitive pulsed magnet for nonlinear and ultrafast spectroscopy in high magnetic fields up to 30 T
We have developed a mini-coil pulsed magnet system with direct optical
access, ideally suited for nonlinear and ultrafast spectroscopy studies of
materials in high magnetic fields up to 30 T. The apparatus consists of a small
coil in a liquid nitrogen cryostat coupled with a helium flow cryostat to
provide sample temperatures down to below 10 K. Direct optical access to the
sample is achieved with the use of easily interchangeable windows separated by
a short distance of ~135 mm on either side of the coupled cryostats with
numerical apertures of 0.20 and 0.03 for measurements employing the Faraday
geometry. As a demonstration, we performed time-resolved and time-integrated
photoluminescence measurements as well as transmission measurements on InGaAs
quantum wells.Comment: 7 pages, 6 figure
Reply to "Comment on `Transition from Bose glass to a condensate of triplons in TlKCuCl'"
Showing low-temperature specific heat and other experimental data and also on
the basis of established physics, we argue against the comment made by Zheludev
and H\"{u}vonnen criticizing our recent study on the magnetic-field-induced
spin ordering and critical behavior in TlKCuCl, which is
described as the Bose glass-condensate transition of triplons.Comment: 2 pages, 2 figures, accepted for publication in Phys. Rev.
Degenerate ground state in the classical pyrochlore antiferromagnet NaMn(CO)Cl
In an ideal classical pyrochlore antiferromagnet without perturbations, an
infinite degeneracy at a ground state leads to absence of a magnetic order and
spin-glass transition. Here we present NaMn(CO)Cl as a new
candidate compound where classical spins are coupled antiferromagnetically on
the pyrochlore lattice, and report its structural and magnetic properties.The
temperature dependences of the magnetic susceptibility and heat capacity, and
the magnetization curve are consistent with those of an = 5/2 pyrochlore
lattice antiferromagnet with nearest-neighbor interactions of 2 K. Neither an
apparent signature of a spin-glass transition nor a magnetic order is detected
in magnetization and heat capacity measurements, or powder neutron diffraction
experiments. On the other hand, an antiferromagnetic short-range order from the
nearest neighbors is evidenced by the -dependence of the diffuse scattering
which develops around 0.85 \AA. A high degeneracy near the ground state
in NaMn(CO)Cl is supported by the magnetic entropy estimated as
almost 4 J K mol at 0.5 K.Comment: 9 pages, 7 figures, accepted to PR
Determination of exchange energies in the sawtooth spin ring {Mo75V20} by ESR
The magnetism of the polyoxometalate cluster {Mo75V20}, containing a sawtooth
ring of 10 corner-sharing triangles located on the equator of the barrel-shaped
molecule, has remained debatable since it is masked by contributions from
impurities as well as temperature-independent paramagnetism. In this article we
demonstrate the usefulness of ESR measurements since the temperature dependence
of the ESR intensity can discriminate between impurity and molecular
contributions. We determine the exchange parameters and therefore also the
low-lying spectrum of {Mo75V20}, especially the low-lying singlet states which
so far have been probed solely by specific heat measurements.Comment: 5 pages, 5 figures, submitted to PR
Heat capacity uncovers physics of a frustrated spin tube
We report on refined experimental results concerning the low-temperature
specific heat of the frustrated spin tube material [(CuCl2tachH)3Cl]Cl2. This
substance turns out to be an unusually perfect spin tube system which allows to
study the physics of quasi-one dimensional antiferromagnetic structures in
rather general terms. An analysis of the specific heat data demonstrates that
at low enough temperatures the system exhibits a Tomonaga-Luttinger liquid
behavior corresponding to an effective spin-3/2 antiferromagnetic Heisenberg
chain with short-range exchange interactions. On the other hand, at somewhat
elevated temperatures the composite spin structure of the chain is revealed
through a Schottky-type peak in the specific heat located around 2 K. We argue
that the dominating contribution to the peak originates from gapped magnon-type
excitations related to the internal degrees of freedom of the rung spins.Comment: 4+ pages, 6 figure
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