4,616 research outputs found
Magnetic-field effects on the in-plane electrical resistivity in the single-crystal LaBaCuO and LaNdSrCuO around : Relating to the field-induced stripe order
Temperature dependence of the in-plane electrical resistivity, , in various magnetic fields has been measured in the single-crystal
LaBaCuO with , 0.10, 0.11 and
LaNdSrCuO with . It has been found that the
superconducting transition curve shows a so-called fan-shape broadening in
magnetic fields for , while it shifts toward the low-temperature side
in parallel with increasing field for and 0.12 where the charge-spin
stripe order is formed at low temperatures. As for , the broadening is
observed in low fields and it changes to the parallel shift in high fields
above 9 T. Moreover, the normal-state value of at low
temperatures markedly increases with increasing field up to 15 T. It is
possible that these pronounced features of are understood in terms of
the magnetic-field-induced stabilization of the stripe order suggested from the
neutron-scattering measurements in the La-214 system. The in
the normal state at low temperatures has been found to be proportional to
ln(1/) for , 0.11 and 0.12. The ln(1/) dependence of is robust even in the stripe-ordered state.Comment: 6 pages, 4 figures, ver. 2 has been accepted for publication in Phys.
Rev.
Thermal Conductivity of the Quasi One-Dimensional Spin System Sr_2_V_3_O_9_
We have measured the thermal conductivity along the [101] direction,
kappa_[101]_, along the [10-1] direction, kappa_[10-1]_, and along the b-axis,
kappa_b_, of the quasi one-dimensional S=1/2 spin system Sr_2_V_3_O_9_ in
magnetic fields up to 14 T, in order to find the thermal conductivity due to
spinons and to clarify whether the spin-chains run along the [101] or [10-1]
direction. It has been found that both kappa_[101]_, kappa_[10-1]_ and kappa_b_
show one peak around 10 K in zero field and that the magnitude of kappa_[10-1]_
is larger than those of kappa_[101]_ and kappa_b_. By the application of
magnetic field along the heat current, the peak of kappa_[10-1]_ is markedly
suppressed, while the peaks of kappa_[101]_ and kappa_b_ little change. These
results indicate that there is a large contribution of spinons to kappa_[10-1]_
and suggest that the spin-chains run along the [10-1] direction.Comment: 3 pages, 4 figure
Single-crystal growth and dependences on the hole concentration and magnetic field of the magnetic ground state in the edge-sharing CuO chain system CaYCuO
We have succeeded in growing large-size single-crystals of
CaYCuO with and measured the
magnetic susceptibility, specific heat and magnetization curve, in order to
study the magnetic ground state in the edge-sharing CuO chain as a function
of hole concentration and magnetic field. In , it has been
found that an antiferromagnetically ordered phase with the magnetic easy axis
along the b-axis is stabilized and that a spin-flop transition occurs by the
application of magnetic fields parallel to the b-axis. The antiferromagnetic
transition temperature decreases with increasing and disappears around 1.4. Alternatively, a spin-glass phase appears around . At where the hole concentration is 1/3 per Cu, it appears that a
spin-gap state is formed owing to the formation of spin-singlet pairs. No sign
of the coexistence of an antiferromagnetically ordered state and a spin-gap one
suggested in CaCuO has been found in
CaYCuO.Comment: 13 pages, 12 figures, 1 tabl
Magnetic-field effects on the charge-spin stripe order in La-214 high-Tc cuprates
Magnetic-field effects on the charge-spin stripe order in La-214 high-Tc
cuprates have been investigated from measurements of the in-plane
electrical-resistivity, Rho_ab_. In La_2-x_Ba_x_CuO_4_ with x=0.10 and
La_2-x_Sr_x_CuO_4_ with x=0.115 where the incommensurate charge peaks are weak
and unobservable in zero field in elastic neutron-scattering measurements,
respectively, the normal-state value of Rho_ab_ at low temperatures markedly
increases with increasing field up to 27 T. For La_2-x_Ba_x_CuO_4_ with x=0.11
and Zn-substituted La_2-x_Sr_x_Cu_1-y_Zn_y_O_4_ with x=0.115 and y=0.02 where
the charge stripe order is fairly stabilized in zero field, on the other hand,
the increase in Rho_ab_ with increasing field is negligibly small. In
conclusion, when the charge-spin stripe order is not fully stable in zero
field, magnetic field operates to stabilize the charge-spin stripe order. The
value of Rho_ab_ increases with increasing field depending on the stability of
the charge stripe order.Comment: 4 pages, 2 figures, Proceedings of Yamada Conference LX on Research
in High Magnetic Fields (RHMF2006) (Satellite of ICM2006
Effective optical identification of type "0-IIb" early gastric cancer with narrow band imaging magnification endoscopy, successfully treated by endoscopic submucosal dissection
Background Endoscopic submucosal dissection (ESD) is currently considered the minimal invasive endoscopic treatment for early gastric cancer. Most superficial gastric neoplastic lesions are depressed type â0-IIcâ (70-80%), while totally flat, classified as type â0-IIbâ early gastric cancer, is rarely reported (0.4%). The aim of the present study was to assess the efficacy of narrow band imaging (NBI) magnification endoscopy in identifying type â0-IIbâ early gastric cancer and ESD treatment with curative intention.Methods Twelve of 615 (2%) patients (10 males, median 72 years), treated by ESD at our center, were diagnosed as type â0-IIbâ gastric cancer. Ten had exclusively type â0-IIbâ, while two had combined types â0-IIb+IIcâ and â0-IIa+IIbâ gastric cancer. Initial diagnosis was made during screening gastroscopy, while NBI magnification endoscopy combined with indigo-carmine chromoendoscopy were also used.Results White light endoscopy showed only superficial redness. One patient with signet-ring carcinoma showed whitish appearance. Indigo-carmine chromoendoscopy showed better visualization, while NBI magnification endoscopy revealed abnormal mucosal microsurface and microvascular findings which enabled border marking. ESD with curative intention was completed without complications. Histological examination showed complete (R0) resection, in 10 patients (83%). One patient with positive margins received additional surgery (8%). Mean procedure time was 149 (range 60-190) min. One to six years post-ESD all patients remain alive.Conclusions ESD is considered a safe and effective curative treatment for type â0-IIbâ gastric cancer, resulting in long-term disease-free survival. NBI magnification endoscopy is effective for accurate optical identification and border marking of type â0-IIbâ early gastric cancer
Real Space Imaging of Spin Polarons in Zn Doped SrCu2(BO3)2
We report on the real space profile of spin polarons in the quasi
two-dimensional frustrated dimer spin system SrCu2(BO3)2 doped with 0.16% of
Zn. The 11B nuclear magnetic resonance spectrum exhibits 15 additional boron
sites near non-magnetic Zn impurities. With the help of exact diagonalizations
of finite clusters, we have deduced from the boron spectrum the distribution of
local magnetizations at the Cu sites with fine spatial resolution, providing
direct evidence for an extended spin polaron. The results are confronted with
those of other experiments performed on doped and undoped samples of
SrCu2(BO3)2.Comment: 9 pages, 11 figures, including supplemental materials. accepted for
publication in PR
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