[en] We have investigated the Hall coefficient in the static stripe phase of La_2-x-yNd_ySr_xCuO₄. We find that a suppression of the Hall effect is observed when the 'metallic' vertical stripes become static and in the x region where the distance between charge stripes is inversely proportional to the doped hole density. In this case each stripe is always 1/4 full with electrons, and possibly possesses particle-hole symmetry

[en] Muon is a magnetic probe available at MLF J-PARC, and is sensitive to local magnetic fields inside materials. Despite its versatility, muon spin relaxation (μSR) technique is less introduced to material scientists compared to neutron diffraction techniques. In this short text, we introduce μSR in comparison to magnetic neutron diffraction with an emphasis of their complimentary features. (author)

[en] The magnetic ground state of an electron-doped cuprate superconductor, Pr_1-xLaCe_xCuO_4+α-δ (x = 0.11, α≅ 0.04), has been studied by means of muon spin rotation/relaxation (μSR) over a wide variety of oxygen depletion, 0.03 ≤ δ ≤ 0.12. The appearance of a weak random magnetism over the entire crystal volume has been revealed by a slow exponential relaxation. The absence of δ-dependence for random magnetism and a multiplet pattern of the muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr³⁺ ions under a crystal electric field. (author)

[en] Spatial phase separation into mesoscopic domains of non-magnetic [superconducting (SC) below T_c ≅ 25.5 K] and two kinds of magnetic phases, one showing disordered spin density wave (d-SDW) order and another associated with glassy weak magnetism (WM), are observed below ∼100 K by muon spin rotation (μSR) in LaFeAsO_1−xF_x for x = 0.057(3), which is near the boundary of these phases on the doping phase diagram. In contrast to the competing order observed in the regular SDW phase of Ba(Fe_1−xCo_x)₂As₂, the WM domain exhibits cooperative coupling of superconducting and magnetic order parameters as inferred from strong diamagnetism and the associated negative shift of μSR frequency just below T_c. (author)

[en] We report on the magnetic phase diagram of a hole-doped cuprate Ca_2-xNa_xCuO₂Cl₂, which is free from buckling of CuO₂ planes, determined by muon spin rotation and relaxation. It is characterized by a quasi-static spin-glass-like phase over a range of sodium concentrations (0.05 ≤ x ≤ 0.12), which is held between the long-range antiferromagnetic (AF) phase (x ≤ 0.02) and the superconducting phase where the system is nonmagnetic for x ≥ 0.15. The obtained phase diagram qualitatively agrees well with that commonly found for hole-doped high-T_c cuprates, strongly suggesting that the incomplete suppression of the AF order for x > 0.02 is an essential features of the hole-doped cuprates. (author)

[en] Slow spin fluctuations (ν < 10¹² s^-1) observed by the muon spin relaxation technique in Y_1-xSc_xMn₂ exhibits a power law dependence on temperature (ν ∝ T^α), where the power converges asymptotically to unity (α → 1) as the system moves away from spin-glass instability with increasing Sc content x. This linear T dependence, which is common to that observed in LiV₂O₄, is in line with the prediction of the intersecting Hubbard chains' model for a metallic pyrochlore lattice, suggesting that the geometrical constraints to t_2g bands specific to the pyrochlore structure serve as a basis of the d-electron heavy-fermion state. (author)

[en] Negative muons are important probes that enable us to investigate non-destructively the elemental composition in thick-layered samples. This method has already shown successful results for the elemental analysis of cultural heritage artifacts. Now, its success attracts also the interest of industrial device developers who want to know non-destructively the inside of a device during switch-on state. At J-PARC MUSE, in response to such needs, we have developed an analysis system with higher detection efficiency to increase opportunities for analyzing many new device samples. This report describes the chamber design and the results obtained from a first test experiment. (author)

[en] Infrared reflectivity spectra of the multilayered HgBa₂Ca_n-1Cu_nO_2n+2+δ(n=2,3,4,and5) are measured. Optical plasma modes associated with the Josephson coupling between CuO₂ planes within a multilayer appear below T_c in the c-axis component of the reflectivity spectrum. For the bilayer and trilayer compound an optical Josephson plasma mode appears at unprecedentedly high frequency, ∼700-800cm^-1, below T_c. The plasma frequencies appreciably decrease in four- and five-layer compounds which indicates the suppression of superconducting order in the inner CuO₂ planes, consistent with the result of NMR experiment.

[en] The most intense pulsed muon beam will be generated by a 3-GeV 333-microA proton beam on a muon target made of 20-mm thick isotropic graphite (IG-430) in J-PARC/MUSE (Muon Science Establishment). The energy deposited by a 1-MW proton beam is estimated to be 3.9 kW on the muon target. The first muon beam was successfully generated on September 26th, 2008. Gradually upgrading the beam intensity, continuous 300-kW proton beam operation was started in January of 2013. The temperatures of the principle components have been measured and recorded through thermocouples and a control system. The lifetime of the muon target is determined by a proton-irradiation damage of the graphite. Even in the 300-kW operation to July of 2013, the radiation damage was anticipated to surpass the lifetime. Therefore, the position of the proton beam has been moved to eight surrounding positions every three weeks to distribute the radiation damage uniformly to a wider area. The position-control is named EXILE operation. The variation of the temperatures at the muon target has been monitored. In this report, the status of proton beam operation and the lifetime extension of the muon target will be described. (author)

[en] The ultra-slow muon beam is expected to be a new probe for surface and interface physics. A new beamline for the ultra-slow muon is now under construction at the J-PARC. Before transporting ultra-slow muons through the transport system, we tuned the system utilizing Li-ions as ultra-slow beam. We successfully transported Li-ions to the end of the beam line. Optimization of the beam transport system is in progress to be ready for generating the ultra-slow muon beam. (author)