Papers by H. Kawano-Furukawa
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2009
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2007
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2007
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2002
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2000
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2000
Natl. Lab., NY, USA-Here we present small angle neutron scattering studies of the vortex lattice ... more Natl. Lab., NY, USA-Here we present small angle neutron scattering studies of the vortex lattice (VL) phase diagram in CeCoIn 5 in the low-field high-temperature regime with H ∥ c which remained unexplored. While previous studies [A. D. Bianchi et.al. Science 319, 177 (2008)] reported the phase boundary between the high-field square → rhombic → hexagonal VLs, the lower boundary between hexagonal → rhombic → square remained unexplored at higher temperatures where only estimates were provided. We have investigated this regime and mapped out these VL transitions. Interestingly, at the base temperature, no rhombic phase is observed but a direct transition from hexagonal to square phase. A possible explanation for this deviation from earlier reports may be that the current measurements were done following a field-ramp at base temperature rather than field-cool used in previous measurements. This indicates a slight hysteresis associated with this transition. While the measured hexagonal to rhombic phase transition agrees with the earlier estimates, the square VL phase occupies a larger region at higher temperatures than previously estimated.
Physica C: Superconductivity, 2003
A field dependence of magnetization of ErNi211B2C at 1.8 K with a field parallel to the b-axis in... more A field dependence of magnetization of ErNi211B2C at 1.8 K with a field parallel to the b-axis indicates that three phase transitions occur at 0.6, 1.1 and 1.9 T. In the present study, we performed neutron diffraction measurements and determined a detailed magnetic structure in a phase at 1.9 K and 0.85 T. Accompanied by odd number higher order peaks there appear strong SDW magnetic peaks with q1=47a∗, indicating that the size of the magnetic unit cell is 7a×b×c.
Physica C: Superconductivity and its Applications, 2010
ABSTRACT
Inelastic neutron scattering was used to study the low temperature spin-wave excitations of the p... more Inelastic neutron scattering was used to study the low temperature spin-wave excitations of the perovkskite Pr_0.7Ca_0.3MnO3 as a function of external magnetic field. At zero field the system is a charge-ordered insulator that exhibits antiferromagnetic order (pseudo CE-type)below T_N=140K and a canted (CA) structure below T_CA=110K. When the high magnetic field is applied the system undergoes an insulator-metal transition dominated by a low-temperature ferromagnetic (FM) phase. We have found that in the metallic FM phase the spin-wave dispersion relation is remarkably similar to other 30compounds, while in the insulating CA phase the dispersion changes dramatically. Research sponsored by the U.S. Department of Energy under contract DE-AC05-00OR22725 with the Oak Ridge National Laboratory, managed by UT-Battelle, LLC.
Journal of Magnetism and Magnetic Materials, 2001
ErNi B C shows the coexistence between weak ferromagnetism and superconductivity below ¹ 5$+ "2.5... more ErNi B C shows the coexistence between weak ferromagnetism and superconductivity below ¹ 5$+ "2.5 K. In the present paper, we studied e!ects of the ferromagnetic order on superconductivity by magnetization measurements. After the zero-"eld cooled (ZFC) procedure, the magnetization curve shows diamagnetic behavior even below ¹ 5$+ , indicating that no spontaneous vortex phase is established in the ZFC procedure. Furthermore, we found that the temperature dependence of H ! shows an abrupt upturn at ¹ 5$+ .
Physical Review B, 2003
We report neutron scattering results on the spin dynamics in the paramagnetic ͑PM͒ and ferromagne... more We report neutron scattering results on the spin dynamics in the paramagnetic ͑PM͒ and ferromagnetic ͑FM͒ states of the 50% hole-doped manganites Pr 1/2 Sr 1/2 MnO 3 and Nd 1/2 Sr 1/2 MnO 3. In the PM phase, these systems exhibit two kinds of diffuse scatterings: an isotropic quasielastic diffuse scattering and a dynamical ridge-type, i.e., two-dimensional FM diffuse scattering. With decreasing temperature, both systems enter the pure FM metallic state, but the spin dynamics in the FM state possess a strong A-type antiferromagnetic feature. In fact, Nd 1/2 Sr 1/2 MnO 3 enters a canted antiferromagnetic phase at lower temperature through a second order phase transition. These behaviors in spin dynamics demonstrate the existence of the static d x 2 Ϫy 2-type orbital ordering in the PM and FM states of 50% hole-doped manganites which have relatively larger one-electron bandwidth.
physica status solidi (a), 2009
The interplay between magnetic order and superconductivity (SC) in RNi2B2C (R = rare earth) has a... more The interplay between magnetic order and superconductivity (SC) in RNi2B2C (R = rare earth) has attracted much attention, because SC coexists with different types of magnetism for R = Dy, Ho, Er and Tm at comparable critical temperatures, and their layered tetragonal structure resembles that of the high temperature superconductors [1]. In contrast to TmNi2B2C, which is superconducting below Tc = 11 K, superconductivity is suppressed in TbNi2B2C. Although the total angular momentum of Tb and Tm is J = 6 in both cases, Tb has a much larger spin component (S=3 and L=3) than Tm (S=1 and L=5) and thereby a significantly larger pair breaking effect on the superconducting Cooper pairs due to the larger spin component (socalled deGennes scaling). Another reason for the suppression of superconductivity may be a change of the lattice dynamics mediating the formation of BCS superconducting state. In non-magnetic compounds with R = Y and Lu [2], and in magnetic R = Er [3] and Ho [4] compounds s...
Physical Review B, 2002
An anomalous phonon peak that appears only in the superconducting state has been reported for non... more An anomalous phonon peak that appears only in the superconducting state has been reported for nonmagnetic intermetallic superconductor RNi 2 11 B 2 C ͑RϭY, Lu͒. In the present paper, we shall demonstrate that another rare-earth borocarbide ErNi 2 11 B 2 C seems to show similar phonon anomalies. A spectral weight transfer from the above-lying TA phonon mode to the aforementioned peak was rather small, but it is consistent with the theoretical prediction for the system with smaller 2⌬/E ph ratio. Combining the present results with those observed in the other borocarbide systems, we suggest that such a phonon anomaly might be a common phenomenon for superconductors with a strong nesting feature of the Fermi surface.
AIP Conference Proceedings, 2006
ABSTRACT The detailed flux line lattice (FLL) structure in YNi2B2C was investigated using small a... more ABSTRACT The detailed flux line lattice (FLL) structure in YNi2B2C was investigated using small angle neutron scattering and the complete H-T phase diagram was determined. The FLL in YNi2B2C shows a change of symmetry only in the low magnetic field region between 0.05 to 0.2 T. The observed square lattice is governed by an anisotropic Fermi velocity. Contrary to the theoretical prediction, a square lattice driven by an anisotropic superconducting gap does not appear below 5 T.
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Papers by H. Kawano-Furukawa