E. Torikai

Muon spin relaxation study on magnetism in high quality single crystal of a high transition temperature superconductor La2−xSrxCuO4−σ (0.11≤x≤0.14)

The positive muon spin relaxation method is applied to probe magnetic ordering in the superconducting phase of a high quality single crystal of La2−xSrxCuO4−σ (0.11≤x≤0.14). The well characterized crystal ofx=0.11 (Tc=34.5 K) with nearly complete flux exclusion exhibits spin freezing at 8K(Tf) with significant spin fluctuation up to 20 K. The onset of spin fluctuation andTf decrease against increasingx towardsx=0.15, suggesting an existence of a magnetic phase boundary aroundx whereTc becomes maximum.

Behavior of the Transverse Spin Component in the Short-Range Ising Spin-Glass Fe0.5Mn0.5TiO3

The spin-glass Fe 0.5 Mn 0.5 TiO 3 ( T SG =21.5 K) has been studied by low-field dc-magnetization, neutron scattering and Mossbauer measurements. The results obtained by the magnetization and neutron scattering measurements indicate that only the longitudinal spin component freezes below T SG . This fact shows that Fe 0.5 Mn 0.5 TiO 3 behaves as a typical Ising spin-glass in both of the measurements. However, the hyperfine fields H hf at Fe nuclei observed by the Mossbauer measurement point to directions other than the hexagonal c -axis in the spin-glass state. This indicates that the transverse spin component contributes to H hf as does the longitudinal one. Combining the results obtained by the three methods, it is concluded that the transverse spin components fluctuate rather incoherently with one another with characteristic times longer than our Mossbauer time scale of ∼10 -7 s.

µCF experiments in thin deuterium films and progress towards slow µ− production

Muon-catalyzed fusion was investigated in thin solid deuterium films to determine the experimental feasibility of slow µ− production by detection of dd fusion protons as well as slow µ− collection utilizing a large-acceptance magnetic spectrometer. The spatial distribution of the fusion reaction in the film was extracted, and an optimum thickness for slow µ− emission was deduced. Collected 10 keV µ− were also successfully detected. However, the dd fusion yield being insufficient, we were not able to distinguish slow µ− via µCF from degraded µ−.

Probing Electron Transfer in DNA – New Life Science with Muons

Using the method of labelled electrons with muons which was first applied to conducting polymers and recently extended to representative electron-transfer proteins, electron transfer phenomena in DNA were successfully studied, for the first time microscopically. The characteristic dependence of muon spin relaxation on inverse magnetic field between 80 and 4000 G strongly suggests an existence of topological one-dimensional (1D) electron transfer along the DNA strands in both A- and B-forms. The low-field behavior, on the other hand, showed remarkable dependence on the molecular conformations.

Muon catalyzed fusion experiments on muonic deuterium atom deceleration in thin solid deuterium films

Abstract Muon catalyzed fusion was investigated in a series of thin solid deuterium films by detecting protons from dd fusion. Two different contributions to the total fusion yield resulting from dμ atoms emitted from a primary hydrogen layer and from incident muons directly stopped in the deuterium film itself were observed. The thickness dependence of the fusion yield suggested the importance of molecular effects in dμ elastic scattering in D 2 .

Measurement of Muonium Hyperfine Splitting at J-PARC

J-PARC K. S. Tanaka1,3, M. Aoki4, H. Iinuma2, Y. Ikedo2, K. Ishida3, M. Iwasaki3, K. Ueno2, Y. Ueno1, T. Okubo2, T. Ogitsu2, R. Kadono2, O. Kamigaito3, N. Kawamura2, D. Kawall8, S. Kanda2,6, K. Kubo7, A. Koda2, K. M. Kojima2, N. Saito2, N. Sakamoto3, K. Sasaki2, K. Shimomura2, M. Sugano2, M. Tajima1, D. Tomono9, A. Toyoda2, H. A. Torii1, E. Torikai5, K. Nagamine2, K. Nishiyama2, P. Strasser2, Y. Higashi1, T. Higuchi1, Y. Fukao2, Y. Fujiwara6, Y. Matsuda1, T. Mibe2, Y. Miyake2, T. Mizutani1, M. Yoshida2, and A. Yamamoto2

Soft X-ray absorption spectra of ilmenite family

We have carried out soft x-ray absorption spectroscopy to study the electronic structure of ilmenite family, such as MnTiO3, FeTiO3, and CoTiO3 at the soft x-ray beamline, BL23SU, at the SPring-8. The Ti and M L2,3 absorption spectra of MTiO3 (M=Mn, Fe, and Co) show spectra of Ti4+ and M2+ electron configurations, respectively. Except the Fe L2,3 spectrum, those spectra were understood within the O(h) symmetry around the transition metal ions. The Fe L3-edge spectrum clearly shows a doublet peak at the L3 edge, which is attributed to Fe2+ state, moreover the very high-resolution the L-edge spectra of transition metals show fine structures. The spectra of those ilmenites are compared.

μ+SR study of Ising spin-glass Fe0.5Mn0.5TiO3

A typical Ising spin-glass Fe0.5Mn0.5TiO3 has been investigated by μ+ spin relaxation measurements. It is found that the local magnetic fields at the μ+ stopping sites appear at a temperature twice as high asTSG. The directional distribution of the local magnetic fields is nearly isotropic, indicating the existence of the transverse spin components. It is clearly demonstrated that the spins fluctuate belowTSG and even at ∼4 K. Taking into account the results obtained by other methods, the main part of the fluctuations is inferred to be due to the transverse spin components and the fluctuation limes at ∼4 K are driven into a range between ∼10−5 and ∼10−7 s.

Behavior of positive muons in highT c superconductors La2?x Sr x CuO4

An unambiguous determination of the μ+ location in the highTc LaSrCuO superconductor is made through zero-field spin relaxation in the paramagnetic phase and its crystal axis dependence by using single crystalline samples. The temperature dependence of the relaxation rates has a maximum between 80 and 150 K, indicating the existence of the onset of quantum diffusion at low temperature.

Interaction of Mu with spin current in GaAs/GaAsP/Si

Abstract We propose a mechanism for probing the polarized electron flow (spin current) by using the spin dependence of the exchange scattering of conduction electrons at Muonium (Mu) and/or muon (μ + ) center resulting from the Pauli exclusion principle. In order to study the feasibility of such a mechanism, we performed the MuSR experiment in Si covered by a strained GaAs overlayer in the presence of photo-induced polarized electrons. The MuSR pattern shows a significant dependence on the wavelength of the laser light. A slight difference in the triplet–singlet population of Mu depending on the polarization direction of the spin current is also observed at the resonance wavelength of the strained GaAs layer. These results suggest the existence of spin-dependent electron scattering at the Mu center.