505 research outputs found
Magnetic ground state of pyrochlore oxides close to metal-insulator boundary probed by muon spin rotation
Magnetism of ruthernium pyrochlore oxides A2Ru2O7 (A = Hg, Cd, Ca), whose
electronic properties within a localized ion picture are characterized by
non-degenerate t2g orbitals (Ru5+, 4d3) and thereby subject to geometrical
frustration, has been investigated by muon spin rotation/relaxation (muSR)
technique. The A cation (mostly divalent) was varied to examine the effect of
covalency (Hg > Cd > Ca) on their electronic property. In a sample with A = Hg
that exhibits a clear metal-insulator (MI) transition below >> 100 K (which is
associated with a weak structural transition), a nearly commensurate magnetic
order is observed to develop in accordance with the MI transition. Meanwhile,
in the case of A = Cd where the MI transition is suppressed to the level of
small anomaly in the resistivity, the local field distribution probed by muon
indicates emergence of a certain magnetic inhomogeneity below {\guillemotright}
30 K. Moreover, in Ca2Ru2O7 that remains metallic, we find a highly
inhomogeneous local magnetism below >>25 K that comes from randomly oriented Ru
moments and thus described as a "frozen spin liquid" state. The systematic
trend of increasing randomness and itinerant character with decreasing
covalency suggests close relationship between these two characters. As a
reference for the effect of orbital degeneracy and associated Jahn-Teller
instability, we examine a tetravalent ruthernium pyrochlore, Tl2Ru2O7 (Ru4+,
4d4), where the result of muSR indicates a non-magnetic ground state that is
consistent with the formation of the Haldane chains suggested by neutron
diffraction experiment.Comment: 12 pages, 13 figure
EFFECTS OF FATIGUE ON THE GROUND REACTION FORCES AND LEG KINEMATICS IN ALL-OUT 600 METERS RUNNING
The purpose of this study was to investigate effects of fatigue on the ground reaction forces and leg kinematics during all-out 600m running, which was performed by eight male middle-distance runners. Their running motion was videotaped (300Hz) and the ground reaction forces were measured (500Hz) at the 150m and 550m marks of the 600m running. From the 150m to 550m mark, running speed significantly decreased (
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