2,916 research outputs found
Magentic-Field Induced Quantum Phase Transition and Critical Behavior in a Gapped Spin System TlCuCl
Magnetization measurements were performed on TlCuCl with gapped ground
state. The critical density and the magnetic phase diagram were obtained. The
interacting constant was obtained as K. The experimental
phase boundary for K agrees perfectly with the magnon BEC theory based
on the Hartree-Fock approximation with realistic dispersion relations and
K. The exponent obtained with all the data points
for K is , which is somewhat larger than theoretical
exponent . However, it was found that the exponent
converges at with decreasing fitting window.Comment: 2 pages, 2 figures, Submitted to Proceedings of International
Conference on Magnetism (ICM2006
Thermodynamic properties of quadrupolar states in the frustrated pyrochlore magnet TbTiO
The low-temperature thermodynamic properties of the frustrated pyrochlore
TbTiO have been studied using the single crystal of
sitting in a long range ordered phase in the - phase diagram.
We observed that the specific heat exhibits a minimum around 2 K and slightly
increases on cooling, similar to a Schottky-like anomaly for canonical spin
ices. A clear specific-heat peak observed at K is ascribable
to the phase transition to a quadrupolar state, which contributes to a
relatively large change in entropy, J Kmol.
However, it is still smaller than for the ground state doublet of the
Tb ions. The entropy release persists to higher temperatures, suggesting strong
fluctuations associated with spin ice correlations above . We
discuss the field dependence of the entropy change for and
.Comment: 6 pages, 2 figure
Observation of Modulated Quadrupolar Structures in PrPb3
Neutron diffraction measurements have been performed on the cubic compound
PrPb3 in a [001] magnetic field to examine the quadrupolar ordering.
Antiferromagnetic components with q=(1/2+-d 1/2 0), (1/2 1/2+-d 0) (d~1/8) are
observed below the transition temperature TQ (0.4 K at H=0) whose amplitudes
vary linear with H and vanish at zero field, providing the first evidence for a
modulated quadrupolar phase. For H<1 T, a non-square modulated state persists
even below 100 mK suggesting quadrupole moments associated with a Gamma3
doublet ground state to be partially quenched by hybridization with conduction
electrons.Comment: Physical Review Letters, in press. 4 pages, 4 figure
Metamagnetic Quantum Criticality Revealed by 17O-NMR in the Itinerant Metamagnet Sr3Ru2O7
We have investigated the spin dynamics in the bilayered perovskite Sr3Ru2O7
as a function of magnetic field and temperature using 17O-NMR. This system sits
close to a metamagnetic quantum critical point (MMQCP) for the field
perpendicular to the ruthenium oxide planes. We confirm Fermi-liquid behavior
at low temperatures except for a narrow field region close to the MMQCP. The
nuclear spin-lattice relaxation rate divided by temperature 1/T1T is enhanced
on approaching the metamagnetic critical field of 7.9 T and at the critical
field 1/T1T continues to increase and does not show Fermi- liquid behavior down
to 0.3 K. The temperature dependence of T1T in this region suggests the
critical temperature Theta to be 0 K, which is a strong evidence that the spin
dynamics possesses a quantum critical character. Comparison between uniform
susceptibility and 1/T1T reveals that antiferromagnetic fluctuations instead of
two-dimensional ferromagnetic fluctuations dominate the spin fluctuation
spectrum at the critical field, which is unexpected for itinerant
metamagnetism.Comment: 5 pages, 4 figures, Accepted by Phys. Rev. Let
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