2,602 research outputs found
NMR study on the stability of the magnetic ground state in MnCrO
The canting angles and fluctuation of the magnetic ion spins of spinel oxide
MnCrO were studied by nuclear magnetic resonance (NMR) at low
temperatures, which has a collinear ferrimagnetic order below and a
ferrimagnetic spiral order below . Contrary to previous reports,
only one spin canting angle of Cr ions was observed. The spin canting angles of
Mn and Cr ions in the ferrimagnetic spiral obtained at a liquid-He temperature
were 43\,^{\circ} and 110\,^{\circ}, respectively. The nuclear spin-spin
relaxation was determined by the Suhl-Nakamura interaction at low temperatures
but the relaxation rate increases rapidly as the temperature
approaches . This indicates that the fluctuation of the spiral component
becomes faster as the temperature increases but not fast enough to leave an
averaged hyperfine field to nuclei in the time scale of nuclear spin precession
in the ferrimagnetic phase, which is on the order of s. The spiral
volume fraction measured for various temperatures reveals that the collinear
and the spiral ferrimagnetic phases are mixed below the transition temperature
of the spiral order. The temperature hysteresis in the volume fraction implies
that this transition has first-order characteristics.Comment: 13 pages, 5 figure
Lie algebra cohomology and group structure of gauge theories
We explicitly construct the adjoint operator of coboundary operator and
obtain the Hodge decomposition theorem and the Poincar\'e duality for the Lie
algebra cohomology of the infinite-dimensional gauge transformation group. We
show that the adjoint of the coboundary operator can be identified with the
BRST adjoint generator for the Lie algebra cohomology induced by
BRST generator . We also point out an interesting duality relation -
Poincar\'e duality - with respect to gauge anomalies and Wess-Zumino-Witten
topological terms. We consider the consistent embedding of the BRST adjoint
generator into the relativistic phase space and identify the
noncovariant symmetry recently discovered in QED with the BRST adjoint N\"other
charge .Comment: 24 pages, RevTex, Revised version submitted to J. Math. Phy
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