Search

The single crystalline and powder samples of multiferroic CuCrO2 have been investigated by 17O NMR techniques in the paramagnetic and magnetically ordered states. The unusual negative hyperfine field on oxygen nuclei, Hhf = −5.2 kOe/µB, has been determined in paramagnetic state. The 17O NMR spectrum in ordered state has a shape typical for incommensurate magnetic structure. It can be well described taking into account only dipole fields which are produced by Cr3+-ions with magnetic moment μ = 2.2 μB. The parameters of the EFG (electric field gradient) tensor – the quadrupole frequency (νQ) and the asymmetry parameter, have been determined. The value of νQ increases monotonously with decreasing temperature in the range 90 K > T > 1.5 K. The estimates of the population of the ligands p – orbitals have been obtained.

A single-crystal momentum-resolved resonant inelastic X-ray scattering (RIXS) experiment under high pressure using an originally designed diamond anvil cell (DAC) is reported. The diamond-in/diamond-out geometry was adopted with both the incident and scattered beams passing through a 1 mm-thick diamond. This enabled us to cover wide momentum space keeping the scattering angle condition near 90°. Elastic and inelastic scattering from the diamond was drastically reduced using a pinhole placed after the DAC. Measurement of the momentum-resolved RIXS spectra of Sr2.5Ca11.5Cu24O41at the CuK-edge was thus successful. Though the inelastic intensity becomes weaker by two orders than the ambient pressure, RIXS spectra both at the center and the edge of the Brillouin zone were obtained at 3 GPa and low-energy electronic excitations of the cuprate were found to change with pressure.

Tris(8-quinolinolato)aluminum(III) (Alq3) shows electronic absorption bands at 378, 360 (in a 1:1 mixed solvent of methanol and ethanol (ME) at 77 K), 334, 316, 300, 263, 255.8, and 233 nm in ethanol at room temperature. According to the polarized fluorescence excitation spectrum together with MO calculations, for instance, the 360 nm band is assigned to an LL CT transition (an intramolecular charge transfer transition between two ligands), and the 378 nm band to an LM/ML CT one (an intramolecular charge transfer transition between ligand and metal). Alq3 shows a broad fluorescence band peaking at around 478 nm in the ME matrix at 77 K. The emission spectrum measured with a phosphoroscope has two emission bands at 567 and 478 nm. The 567 nm band accompanies vibronic bands at 578 and 605 nm, being safely assigned to a phosphorescence of Alq3. The lifetimes of the 478 and 567 nm bands are both 5.4 ms. The lifetime of the 478 nm band together with the band position and its band shape indicate that this band can be assigned to a delayed fluorescence.

It has been observed for the binary systems of oriented nematic hosts and nonmesomorphic guests (substituted anthraquinones) that the orientational orders of amino-substituted anthraquinones ascend with increasing guest concentrations. A new quantitative and experimental procedure has been proposed for obtaining the host–guest isotropic dispersion, isotropic electrostatic, anisotropic dispersion, and anisotropic electrostatic interaction energies. Among these four host–guest interaction energies, the host–guest isotropic dispersion interaction energy alone is demonstrated to be well correlated with the concentration dependence of the orientational order of the guest. A model is also proposed for the cooperative and isotropic host–guest interaction.

115In-NMR measurements of the unconventional superconductor CeCoIn $$_5$$ reveal an unusual temperature dependence of the Knight shift near the upper limit of $$H_{c2}$$ . From a simulation analysis, the present NMR study provides a direct evidence at a microscopic point of view that the Fulde–Ferrell–Larkin–Ovchinikov (FFLO) state is realized at the high field SC phase in CeCoIn $$_5$$ .

We have investigated the metal-insulator transition (MIT) of CuIr2S4 by a high resolution NMR measurement. The Cu-NMR spectrum below T MI is broadened and split into four Cu signals with sizable electric quadrupole interactions. The NMR results are consistent with the charge ordering of Ir^3+ and Ir^4+ and the spin dimerization of Ir^4+ spins, as revealed by a recent X-ray study.

Time-resolved transient absorption spectra of photo-irradiated 2,2′-pyridil were measured in PVA films. The broad bands at 552 and ∼455 nm, appearing just after photo-excitation of 2,2′-pyridil, ar...

Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The 1H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the 1H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of CS symmetry, in which the benzene molecule mainly interacts with the π electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the 1H NMR spectral shifts mentioned above and the experimentally predicted CS structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure.

Spatially-resolved NMR is used to probe the magnetism in the vortex state of nearly optimally doped high-Tc cuprate Tl2Ba2CuO6+δ ( T c =85 K ). We found that (1) the nuclear spin–lattice relaxation rate T1−1 at 205 Tl is extremely enhanced toward the vortex core and (2) T1 process become largely inhomogeneous in the vortex state and (3) the temperature dependence of T1−1 at the vortex core region shows a peak at T∼20 K . These results indicates a clear evidence of the antiferromagnetic (AF) order inside the vortex core, and that the suppression of the d-wave superconducting order parameter leads to the nucleation of islands with AF order.

By using spatially-resolved NMR method, we observed nuclear spin-lattice relaxation rate (1/T1) of the vortex state to probe antiferromagnetic correlations at the vortex core. We found that the temperature dependence of 1/T1 shows a peak, which results from a local antiferromagnetic ordering of Cu spins in the vortex core.

We report a site-selective 17 O spin–lattice relaxation rate T 1 −1 in the vortex state of YBa 2 Cu 4 O 8 . We found that T 1 −1 at the planar sites exhibits an unusual nonmonotonic NMR frequency dependence. Based on T 1 −1 in the vortex core region, we establish strong evidence that the local density of states within the vortex core is strongly reduced.

From high resolution measurements of the nuclear quadrupole frequencies we obtain experimental evidence that a vortex in high Tc superconductors (HTSC) traps a finite electric charge. In slightly overdoped YBa2Cu3O7 the vortex is negatively charged by trapping electrons, while in underdoped YBa2Cu4O8 it is positively charged by expelling electrons. The sign of the trapped charge is opposite to the sign predicted by the conventional BCS theory. Moreover, in both materials the deviation of the magnitude of the charge from the theory is significant. These features can be attributed to the novel electronic structure of the vortex in HTSC

The electronic absorption and X-ray photoelectron spectra of N,N′-disalicylidenetrimethylenediaminatocopper(II) ([Cu(saltn)]) and N,N′-disalicylidene-trans-1,2-cyclohexanediaminatocopper(II) ([Cu(salchx)]) were measured. From these results and from informations derived from MO calculations the electronic structure of the complexes was clarified. Each electronic absorption band which can be assigned to the ππast; or ML/LMCT transition of [Cu(saltn)] or [Cu(salchx)] observed in the wavelength region of 450–200 nm appears at the almost same frequency as the corresponding band of N,N′-disalicylideneethylenediaminatocopper(II) ([Cu(salen)]) in solution. The LLCT bands (the intramolecular CT band between two π-electronic systems separated by saturated hydrocarbon chains such as ) also appear at nearly the same positions (ca. 245 nm) for [Cu(salchx)], [Cu(saltn)], and [Cu(salen)]. The locations of the dd transition and the intensity of the ML/LMCT transition of [Cu(saltn)] are significantly different from those of [Cu(salen)] and [Cu(salchx)]. These differences may arise from the strengths of the interaction between metal and ligand.

55 Mn nuclear magnetic resonance (NMR) measurements have been carried out in Mn12 clusters in order to investigate microscopically the magnetic properties of inner spin structure of the molecule in its high spin S=10 ground state. The external magnetic field dependence of 55 Mn-NMR spectrum gives a direct confirmation of the internal magnetic structure of the Mn12 cluster, in which spin moments of Mn 4+ (S=3/2) ions are polarized antiparallel to that of Mn 3+ (S=2) ions. It is proved that the microscopic spin configuration rotates rigidly when a field up to 8T is applied perpendicular to the easy-axis. Mn12 cluster Internal structure 55 Mn-NMR

The proton nuclear spin-lattice relaxation rate 1/ T 1 has been measured as a function of temperature (T=1.4-4.2K) and magnetic field (H=0.6-5T) in the Fe8 cluster in its high spin S=10 ground state. The strong temperature and field dependence of 1/ T 1 can be fitted well by using a simple model in terms of the thermal fluctuations of the total spin S=10 of the cluster originating from the spin-phonon interactions. 1/ T 1 data of protons in a partially deuterated Fe8 cluster is also reported. The results indicate that the spin phonon coupling constant is not affected by the change of mass of the isotopes in the Fe8 cluster. Nanomagnet Fe8 cluster nuclear magnetic resonance

The electronic absorption spectra of N,N′-bis(2-aminobenzylidene)ethylenediaminatocopper(II) (abbreviated to [Cu(amben)]) were measured in ethanol and in a KBr disk. From these spectral data together with the polarization spectrum in a stretched PVA film, the X-ray photoelectron spectra, and a VESCF-MO-CI calculation, the electronic structure of [Cu(amben)] has been clarified. The reduced polarization spectrum shows that [Cu(amben)] has longer-molecular axis (y) polarized bands at 438, 300, 280, 257.7 and 222 nm, and shorter ones (z) at 418, 280, 260, 242.5 and 224 nm. The 300 nm band is assigned to an overlap of the calculated ππ*3 and ππ*4 transitions, which are charge transfer transitions between the two π-electronic systems localized almost independently on the 2-aminobenzylideneimino groups. The solid-state electronic absorption bands, measured in a KBr disk, of [Cu(amben)] are red-shifted by 2-16 nm, and considerably broadened compared with those in ethanol, indicating that the [Cu(amben)] molecules...

We have systematically measured the thermal conductivity κ of Sr 14- x A x Cu 24 O 41 (A=Ca, La: 0≤ x ( Ca) ≤9: 0 ≤ x ( La) ≤5) single crystals, in order to investigate the spin gap and hole pairin...

The present NMR study indicates an appearance of finite hyperfine fields coupled to incommensurate antiferromagnetic order of the Ce moments in CeCoIn 5 . The magnetic order is never observed in the normal state and also in the BCS state, but appears only inside the novel superconducting phase. Strong field dependence of the ordered magnetic moments indicates the coexistence of the incommensurate SDW order and an modulated SC (FFLO) state.

The absorption and fluorescence spectra of 1-aminoanthracene (AA) in various solvents have been compared with those of 1-dimethylaminoanthracene (DMAA). This comparison has demonstrated that the amino group of AA in the ground electronic state acts as a proton-acceptor to form the A-type hydrogen bond with alcohol, while that of AA in the excited electronic state acts as a proton-donor to form the B-type one. In the cyclohexane-ethanol mixed solvent, the solute-solvent configuration for the fluorescing excited state of AA changes with the ethanol concentration; it keeps the same type of hydrogen bond with ethanol as that (A-type) in the ground electronic state in the lower ethanol concentrations up to 0.2% and exhibits an intramolecular-like rearrangement of the A-type hydrogen bond into the B-type one in the ethanol concentration range of 0.2—1%. This hydrogen bond rearrangement occurs in cooperation with a bulk reorientation of solvent molecules in the range of 1—100%. AA forms the hydrogen-donor-accept...

Long-range antiferromagnetic (AF) order in the doped spin ladder compound of Sr2.5Ca11.5Cu24O41 is investigated by heat capacity, magnetization and Cu-NMR/NQR measurements. We suggest that this AF order is primarily responsible for the chain Cu moments

Hole-doping effects are investigated by Cu-NMR for single crystal of Sr{sub 14{minus}x}Ca{sub x}Cu{sub 24}O{sub 41}. The charge order of Cu{sup 2+} and Cu{sup 3+} and spin dimer ground state in the chain of Sr{sub 14}Cu{sub 24}O{sub 41} are proved by NMR study. The magnetic order of Cu spins in the chain and also the field-induced staggered moments at the ladder Cu site are confirmed for 3 {le} x {le} 6 of Sr{sub 14{minus}x}La{sub x}Cu{sub 24}O{sub 41}.

A Fulde–Ferrell–Larkin–Ovchinnkov (FFLO) state is investigated in the quasi-2D heavy fermion CeCoIn 5 by a 115In NMR study in both perpendicular and parallel field to the ab-plane. Although the topology of the phase transition lines in the H – T phase diagram of the FFLO state is identical for both configurations, there are several remarkable differences between them.

The 31 P nuclear magnetic resonance ( 31 P-NMR) and muon spin relaxation (µSR) of the filled skutterudite compound SmRu 4 P 12 have been carried out. The line width of the 31 P-NMR spectrum rapidly increases below the metal–insulator transition temperature T MI but not below the Neel temperature T N . The temperature dependence of the spin–lattice relaxation rate shows a successive anomaly at T MI and T N . The µSR measurements indicate that a static internal field appears below T MI , which means that the ordering below T MI is a magnetic ordering with the time reversal symmetry breakdown. These results support a scenario that a magnetic octupolar ordering occurs below T MI in SmRu 4 P 12 .

Josephson plasma excitation of Bi2Sr2CaCu2O8+δ in parallel magnetic fields is studied by angular alignment with ∼0.02° precision. A disappearance of the resonance has been found for angles within θ ∼ 0.2° (θ is an angle between the field and the CuO2-plane). The origin of the phenomenon is discussed in terms of the Josephson plasma oscillation and Josephson vortex oscillation modes.

Single crystals of the heavily Pb-substituted Bi-2201 phase with a composition of Bi 1.80 Pb 0.38 Sr 2.01 CuO 6+δ as determined by fluorescence X-ray composition analysis were grown to a typical planar shape of 6 × 3 × 0.03 mm 3 by using a floating zone method. These crystals with the highest Pb content ever reported are free from any structural modulation as examined by transmission electron microscopy, and the orthorhombic lattice parameters are a = 5.300(3) A , b = 5.392(3) A , and c = 24.603(5) A (V = 703.2 A 3 ) . Their superconducting properties can be modified within the over-doped region in such a way that the transition temperature, T c , is raised from 3 K for the as-grown crystals to 23 K by annealing at 550°C for 2 weeks in a vacuum of ∼ 10 −4 Pa. The out-of-plane resistivity of the as-grown crystals remains metallic down to 20 K, while it becomes semiconductive below 160 K after the annealing.

Carrier doping effects on spin dynamics in ${\mathrm{Sr}}_{14\ensuremath{-}x}{A}_{x}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ ( $A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{Ca}$, Y, and La) are investigated by Cu NMR and NQR. The energy gaps in the spin excitation spectra (spin gap) are confirmed to be $\ensuremath{\Delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}140\mathrm{K}$ for the Cu${\mathrm{O}}_{2}$ chain and $\ensuremath{\Delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}470\mathrm{K}$ for the C${\mathrm{u}}_{2}$${\mathrm{O}}_{3}$ ladder in S${\mathrm{r}}_{14}$C${\mathrm{u}}_{24}$${\mathrm{O}}_{41}$. The spin gap for the ladder increases with the Y and La substitutions for Sr (up to $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$), while it decreases with increasing x in ${\mathrm{Sr}}_{14\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ and seems to collapse around $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13$ of the Ca substitution. Hole-doping effects on the spin gaps for the ladder configuration are interpreted in terms of magnon and hole-depairing excitations for the spin $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\frac{1}{2}$ ladder.

We have investigated spin dynamics of both the ladder and the chain sites in Sr 14 Cu 24 O 41 by Cu-NMR and Cu-NQR. From the NMR shift, K spin , and nuclear spin-lattice relaxation time, T 1 , the energy gaps in the spin excitation spectrum are confirmed to be Δ=140 K for the chain site and Δ=470 K for the ladder site for Sr 14 Cu 24 O 41 . Doping effects on the spin gaps and electric field gradient at the Cu sites were also investigated by the substituting of Ca, Y and La for Sr. The spin gap of the ladder site decreases with increasing x for Sr 14- x Ca x Cu 24 O 41 and seems to collapse at around x =13 for Ca substitution.

A new strontium vanadium sulfide, SrV 2 S 5 , has been successfully synthesized. The powder X-ray diffraction pattern has been indexed on the basis of a rhombohedral cell with hexagonal lattice constants of a = 3.314 and c = 35.023 A. However, the electron diffraction measurements show that the structure is more complex and has an unidentified superstructure. The specimens of SrV 2 S 5 show no indication of superconductivity down to 2 K. The resistivity is low, semiconductive, and weakly dependent on temperature above 50 K. The magnetic susceptibility is nearly temperature independent above ∼80 K; below 50 K it shows extremely small Curie–Weiss-like behavior. Temperature dependence of the Knight shift in vanadium NMR shows a broad peak around 80 K.

We have investigated antiferromagnetic nuclear resonance (AFNMR) for Cu-site as well as nuclear magnetic (NMR) and quadrupolar (NQR) resonances for La, Nb, Ga-sites in antiferromagnetic insulators RBa 2 Cu 2 NbO 8 ( R=La, Pr, Nd) and RSr 2 Cu 2 GaO 7 ( R=La, Pr, Nd, Y). Hyperfine magnetic fields at the Cu-site are very close to values published for RBa 2 Cu 3 O 6 analogs. Quadrupolar frequencies for Cu in RSr 2 Cu 2 GaO 7 are also close to those for RBa 2 Cu 3 O 6 but in RBa 2 Cu 2 NbO 8 these values are about 50% higher. Axially symmetric electric field gradient at the La and the Nb-sites in RBa 2 Cu 2 NbO 8 and asymmetric one at the La and Ga-sites in RSr 2 Cu 2 GaO 7 are in accord with their structures. Split NQR spectrum for Ga in NdSr 2 Cu 2 GaO 7 evidences the different Cu-AF spin stacking sequence in this material. Possible cation disorder in RSr 2 Cu 2 GaO 7 is discussed.

Using 31 P-nuclear magnetic resonance (NMR), low-energy spin excitations are investigated in both (VO) 2 P 2 O 7 and VO(HPO 4 )0.5H 2 O, in which V 4+ ( S =1/2) ions take ladder and dimer (isolated pair) configurations, respectively. Temperature ( T ) dependences of Knight shift ( K ) and nuclear spin-lattice relaxation time ( T 1 ) in the two compounds show a thermally activated behavior originating from the spin gap formation in the low energy spin excitation. The most distinct difference appears in the T -dependence of ( T 1 T K ) -1 at low temperature, i.e., the T -independent behavior in the dimer system and the large decrease below the order of the spin gap in the ladder system. These experimental results suggest that the spin gap Δ is independent of wave vector q in the case of the dimer system, while Δ depends on q for the spin ladder system. Resonance frequency dependence of T 1 in the temperature regions of both T Δ is also discussed.

We study the microwave response perpendicular to the superconducting layers of high temperature superconductors in a wide range of temperatures and fields. A novel microwave response,i.e. Josephson plasma resonance, shows up in the superconducting state of Bi2Sr2CaCu2O8+δ. This resonance enable us to measure the magnitude of interlayer phase coherence quantitatively. Josephson plasmon is shown to interact strongly with the vortices. Therefore it provides a new powerful tool to probe the vortex state. The vortex state of high temperature superconductors is discussed in the light of the interlayer phase coherence.

κ-(BEDT-TTF) 2 X salts show the variety physical properties from the superconductivity to the magnetic ordering. It is important to investigate the characters of κ-(BEDT-TTF) 2 X from microscopic probes, systematically. 13 C-NMR is a one of the most powerful tool for this aim. In order to study the variety physical properties on of κ-(BEDT-TTF) 2 X, We performed single crystal 13 C-NMR works on deuterized samples, alloy system etc. Here we report especially about κ-(BEDT-TTF) 2 Cu 2 (CN) 3 from our a several approaches in this proceedings. Recently, for κ-(BEDT-TTF) 2 Cu 2 (CN) 3 , the magnetic frustrations are pointed out. However, we found the evidence of the electron localization phenomenon on this salt from 13 C-NMR work.

The system of the deuterated κ-(BEDT-TTF-d[n,n]) 2 Cu[N(CN) 2 ]Br is situated in the critical region between the superconducting(SC) phase and the antiferromagnetic insulator (AFI) phase, and is just on the Mott type critical boundary of paramagnetic metal (PM) phase and paramagnetic insulator (PI) phase. We perform two single-crystal 13 C-NMR studies on the non and the fully deuterated κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br at low temperature with the applied field 9.4T. We found two new experimental results. One is that the phase separation is found in κ-(BEDT-TTF-d[0,0]) 2 Cu[N(CN) 2 ]Br salt, like partially deuterated κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br salt. The other is that the phase separation is observed at around T* with the applied field parallel to the conducting layer, unlike partially deuterated κ-(BEDT-TTF-d[n,n]) 2 Cu[N(CN) 2 ]Br. The former result suggests the field induces AF transition. the latter result suggests there is the field direction dependence of the M-I phase separation behavior in κ -(BEDT-TTF-d[4,4]) 2 Cu[N(CN) 2 ]Br.

An extensive study of electrical resistivity, ac magnetic susceptibility, magnetization, specific heat, and NMR has been made on high purity samples of the spinel compounds ${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$ and ${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$. The superconducting transitions occur at 4.70 K in ${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$ and 3.48 K in ${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$. The magnetic susceptibilities show perfect diamagnetism in both compounds. Upper critical fields at T=0 are estimated to be 20.0 and 4.40 kOe, the lower critical fields at T=0 are 70 and 95 Oe, respectively. The thermodynamic critical fields at T=0 are 704 Oe (${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$) and 445 Oe (${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$). These values are obtained from the temperature dependence of the free energy. These compounds are type-II superconductors with Ginzburg-Landau parameters \ensuremath{\kappa}=21 (${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$) and \ensuremath{\kappa}=6.6 (${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$) at T=0. The electron-phonon coupling constants, ${\ensuremath{\lambda}}_{\mathrm{ep}}$=0.68 (${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$) and ${\ensuremath{\lambda}}_{\mathrm{ep}}$=0.64 (${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$), are obtained using the McMillan formula. The copper nuclear-spin-relaxation rate as a function of temperature shows a pronounced coherence peak just below ${\mathit{T}}_{\mathit{c}}$ for ${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$. Experimental results are analyzed on the basis of the BCS theory. These compounds exist between weak- and intermediate-coupling superconductors which are driven by electron-phonon interaction. The Debye temperatures FTHETA of these materials are 230 K (${\mathrm{CuRh}}_{2}$${\mathrm{S}}_{4}$) and 211 K (${\mathrm{CuRh}}_{2}$${\mathrm{Se}}_{4}$).

Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12][Br8 9H2O], in short Fe8, have been performed at 1.5 K in a powder sample aligned along the main anisotropy z axis, as a function of a transverse magnetic field (i.e., perpendicular to the main easy axis z). A big enhancement of 1/T1 is observed over a wide range of fields (2.5-5 T), which can be attributed to the tunneling dynamics; in fact, when the tunneling splitting of the pairwise degenerate m=+-10 states of the Fe8 molecule becomes equal to the proton Larmor frequency a very effective spin lattice relaxation channel for the nuclei is opened. The experimental results are explained satisfactorily by considering the distribution of tunneling splitting resulting from the distribution of the angles in the hard xy plane for the aligned powder, and the results of the direct diagonalization of the model Hamiltonian., Comment: J. Appl. Phys., in press

Synthesis of deuterated and 13 C -enriched BEDT-TTF, and the results of 13 C NMR (nuclear magnetic resonance) measurement of κ-(BEDT-TTF)2Cu[N(CN)2]Br salt are reported where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. We synthesized the BEDT-TTF molecule 13 C -enriched on only one side of the central carbon sites. By using this molecule, we could avoid the Pake doublet and estimate the density of states from the Knight-shift and the spin–lattice relaxation rate. The reduced mass effect predicted from the specific heat measurement was not observed in the 13 C NMR measurement.

The muon spin rotation (μ +SR) and NMR measurements provides clear evidences of the antiferromagnetic order of Cu-moment below 35 K for La2−x Ba x CuO4 and below 15 K for La2−x Sr x CuO4 in the narrow range ofx where the high-T c superconductivity (SC) is suppressed remarkably. The results suggest that the freezing of spin fluctuations of Cu-moment is relevant to the local suppression of SC under an change of the electronic state coupled with the lattice instability.

Zero field positive muon spin rotation method (μ +SR) is applied on La2−x Sr x CuO4 around forx=0.12 at which the high-T c superconductivity (SC) is suppressed. The magnetically ordered state of Cu-moments, which is not a spin glass state but an antiferromagnetic like state, appears below 15 K for 0.105≤x≤0.120. The magnetic phase boundary is very similar to the one of the La2−x Ba x CuO4 in which the structural transition from the low temperature orthorhombic (LTO) phase to the low temperature tetragonal (LTT) phase is observed aroundx=0.12. The present study suggests that there is no big difference of the electronic state of the CuO2 plane between the La-Ba system and the La-Sr system and that the magnetic ordering of Cu-moments plays an important role for the suppression of the high-T c SC aroundx=0.12 in both of the systems, although the LTO-LTT structural transition has not been observed yet in the La-Sr system.

Muon spin rotation (μ+SR) measurement provides clear evidence of the antiferromagnetic order of Cu moments below 35 K for La2−xBaxCuO4 and below 15 K for La2−xSrxCuO4 in the narrow range ofx where the high-Tc superconductivity (SC) is suppressed remarkably. The results suggest that the change of the electronic state coupled with the lattice instability is relevant to the local suppression of SC and freezing of spin fluctuations of the Cu moment.

We report an experimental evidence that a vortex in the high temperature superconductors traps a finite electric charge from the high resolution measurements of the nuclear quadrupole frequencies. In slightly overdoped YBa 2 Cu 3 O 7 the vortex is negatively charged by trapping electrons, while in underdoped YBa 2 Cu 4 O 8 it is positively charged by expelling electrons. The sign of the trapped charge is opposite to the sign predicted by the conventional BCS theory. Moreover, in both materials, the deviation of the magnitude of the charge from the theory is also significant.

We have measured the anisotropy ratio of the 63 Cu(2) nuclear spin-lattice relaxation rate ( W ) for YBa 2 Cu 3 O 6.89 in the superconducting state. The anisotropy ratio is defined as the ratio of the relaxation rates W ab to W c in magnetic fields perpendicular and parallel to the crystal c -axis, respectively. Below T c we find that the anisotropy ratio ( R ) is significantly temperature dependent in high magnetic fields (7–7.5 T).

Muon spin rotation (μSR) is applied to La2−xBa x CuO4 aroundx=0.12 where the superconductivity (SC) is suppressed remarkably. The magnetic ordering of Cu-moments appears below 35 K in the narrow range ofx where a lattice instability from the low temperature orthorhombic (LTO) to the low-temperature tetragonal (LTT) structure exists. The present study suggests strongly that the magnetic ordering of Cu-moments is an important factor in the suppression of high-Tc superconductivity aroundx=0.12 in La2−xBa x CuO4. Similar results are obtained for the La2−xSr x CuO4 and La2−x−ySr x Nd y CuO4 systems.

We present In NMR measurements in a novel thermodynamic phase of CeCoIn5 in high magnetic field, where exotic superconductivity coexists with the incommensurate spin-density wave order. We show that the NMR spectra in this phase provide direct evidence for the emergence of the spatially distributed normal quasiparticle regions. The quantitative analysis for the field evolution of the paramagnetic magnetization and newly-emerged low-energy quasiparticle density of states is consistent with the nodal plane formation, which is characterized by an order parameter in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The NMR spectra also suggest that the spatially uniform spin-density wave is induced in the FFLO phase., Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Lett

We have performed magnetization and 27 Al- and 11 B-NMR measurements of Mg 1- x Al x B 2 with x =0, 0.16, 0.22, 0.30, and 0.45 in both the normal and superconducting (SC) states. In the normal state, the temperature-independent values of 1/ T 1 T of 27 Al and 11 B decrease with increasing x . The 1/ T 1 of 27 Al decreases exponentially with temperature in the SC state followed by the appearance of a tiny coherence peak just below T c . The 1/ T 1 of 11 B for x ≥0.22 shows no gap behavior below T c , indicating the large reduction in superconducting gap with x at the B site. The temperature dependence of 1/ T 1 T in the SC state is quantitatively analyzed using a s wave SC model with two gaps of 2Δ/ k B T c ∼1.5 and 4. The present results show that Δ σ is markedlly deceases with increasing x , namely, with σ band filling by electron doping, providing convincing evidence for two SC gaps with spin singlet s -wave pairing in Mg 1- x Al x B 2 .

Positive muon spin rotation (µ + SR) is applied to La 2- x Ba x CuO 4 around x =0.12, where superconductivity is suppressed remarkably. The magnetic ordering of Cu-moments appears below 35 K in the narrow range of 0.11≦ x ≦0.135, where the transition from the low-temperature orthorhombic (LTO) to the low-temperature tetragonal (LTT) structure exists. The present study suggests strongly that the magnetic ordering of Cu-moments plays an important role in the suppression of the high- T c superconductivity around x =0.12 in La 2- x Ba x CuO 4 .

Anomalies of heat capacity and thermal expansion have been observed near x =0.12 in La 2- x Ba x CuO 4 . The anomalies are ascribed to the low-temperature structural transition. We determine accurately the phase baundary as a function of x . Widely broadened Cu-NQR spectra for x

Topological effects on magnetic properties were revealed by an experimental and theoretical investigation on two Cr-based ring-shaped nanomagnets Cr8 and Cr8Cd as model systems for ``closed'' and ``open'' antiferromagnetic rings, respectively. The detailed structures of the low-lying energy levels in terms of the total spin were established directly by high-field magnetization measurements up to 57 T. All the differences observed in the magnetization curve of the two systems can be interpreted by the different topology of the magnetic coupling scheme whereby the experimental observations are well reproduced by theoretical calculations.

Split spectra of Cu nuclear quadrupole resonance (NQR) in the chain (Cu(1)) site of the antiferromagnetic YBa 2 (Cu 1- x T x ) 3 O 6 (T=Fe, Co, and Ni) show that the spin alignment of Cu moments in the CuO 2 plane changes at a critical concentration of the substitution of Cu by T. The spin structure of the low-temperature magnetic phase is discussed.