Kazuki Ohishi

Magnetic Properties in Phase IV of Ce0.7La0.3B6 Studied by Muon Spin Relaxation

The magnetic properties of Ce 0.7 La 0.3 B 6 single crystal have been studied by muon spin relaxation (µSR). The absence of a clear muon spin precession under zero external field in phase IV indicates that no commensurate long-range magnetic order is present in this phase. Moreover, the time spectra under a longitudinal field strongly suggests that there are two sources of local fields exerting coherently on muons in phase IV. It was inferred from the muon Knight shift under a transverse field that the direction of the effective internal magnetic field probed by muon exhibits a marked change between phase III and IV.

Quasiparticle Excitations outside the Vortex Cores in MgB2 Probed by Muon Spin Rotation

The magnetic penetration depth λ in the mixed state of MgB 2 has been determined microscopically from the field distribution around magnetic vortices probed by muon spin rotation. Both the temperat...

Anomalous quasiparticle excitations in Y(Ni1−xPtx)2B2C

Abstract We have found that although the magnetic penetration depth λ increases linearly in H in YNi2B2C, λ in Y(Ni0.8Pt0.2)2B2C was found to be independent of H for H⩽0.4Hc2, suggesting that the superconducting gap is effectively isotropic. These results are consistent with the change in the structure of order parameter suggested by photoelectron spectroscopy. However, λ in the Pt-doped sample is about 1.27 times larger than that estimated for an impurity effect, suggesting that the quasi-particles are not completely localized inside the vortex cores.

Anomalous field dependence of the vortex-core radius and magnetic penetration depth in YNi2B2C probed by μSR

Abstract Muon spin rotation measurements were performed to deduce the magnetic penetratioin depth λ and vortex core radius ρv in the mixed state of YNi2B2C for H c 1 ⪡H≦0.7 H c 2 . A preliminary analysis based on the modified London model shows that ρv decreases steeply with increasing H, while λ increases linearly in H.

Magnetic penetration depth of a new boride superconductor Re3B

Abstract We have performed muon spin rotation (μSR) measurements in polycrystalline Re 3 B to elucidate the structure of quasiparticle excitations which are related to the pairing symmetry. The temperature and magnetic field dependence of the penetration depth λ suggest an isotropic order parameter with the BCS mechanism.

Spatially Modulated Antiferromagnetism in Sr 2.5Ca 11.5Cu 24O 41 Probed by Muon Spin Relaxation

A strongly modulated Neel order has been inferred from muon spin relaxation (µSR) measurement in Sr 2.5 Ca 11.5 Cu 24 O 41 below T N = 2.2 ±0.1 K in conjunction with the previous result of neutron ...

Anomalous local magnetic shielding effect at muon site in Sr2.5Ca11.5Cu24O41 and Ce0.99Cu2.02Si2

Abstract We present that the time structure of ZF- and LF-μSR spectra in the magnetic phase of Sr2.5Ca11.5Cu24O41 and in the A-phase of Ce0.99Cu2.02Si2 shares a number of common features. In particular, the magnitude of local magnetic field at the muon site estimated from ZF-μSR is seemingly far smaller than that estimated by LF-quenching experiment. As a microscopic model of such an anomalous local magnetic shielding, we discuss the possibility of muon-induced local magnetism due to the magnetic instability of frustrated spin systems near the quantum critical point.

The magnetic ordering in the spin ladder compound Sr2.5Ca11.5Cu24O41

Abstract μSR and neutron experiments on Sr2.5Ca11.5Cu24O41 single crystal have been performed. The time-dependenet muon polarization shows a significant change at around T N ≃2.1 K indicating the onset of magnetic long-range order. Considering both the μSR and neutron scattering data, a possible magnetic structure on the chain and ladder sites has been proposed. However, the lack of coherent μSR precession signal strongly suggests that the distribution of the internal field is not homogeneous. This can be interpreted in line with the scenario that the singlet state and antiferromagnetic order coexist at ambient pressure and these localized hole pairs begin to move under pressure, resulting in the occurrence of superconductivity.

Magnetism in Ce2Rh(In,Sn)8 heavy-fermion compound

Measurements of muon spin relaxation have been performed on Ce2RhIn8?xSnx (x = 0.0,0.1,0.5 and 0.7) single crystals down to 0.3 K. A clear muon spin precession signal was observed in x = 0.0 and 0.1 samples due to antiferromagnetic ordering with magnetic volume fraction of ~75% below TN. While an increase of relaxation rate was observed in x = 0.5 below 0.5 K, no precession signal was observed, suggesting the suppression of antiferromagnetism with increasing Sn concentration.

Physical Properties in Flux Line Lattice State in MgB2 Probed by µSR

We have performed muon spin rotation (µSR) measurements to deduce the magnetic penetration depth λ in the flux line lattice state of MgB 2 microscopically. It is observed that λ shows a quadratic temperature dependence which is predicted for the case of superconducting gap with line nodes. Furthermore, it clearly exhibits a strong field dependence, where λ increases almost linearly with H . These results strongly suggest that the superconducting order parameter in MgB 2 is highly anisotropic.