423 research outputs found
Spin Susceptibility in the Superconducting state of Ferromagnetic Superconductor UCoGe
In order to determine the superconducting paring state in the ferromagnetic
superconductor UCoGe, ^{59}Co NMR Knight shift, which is directly related to
the microscopic spin susceptibility, was measured in the superconducting state
under magnetic fields perpendicular to spontaneous magnetization axis:
^{59}K^{a, b}. ^{59}K^{a, b} shows to be constant, but does not decrease below
a superconducting transition. These behaviors as well as the invariance of the
internal field at the Co site in the superconducting state exclude the
spin-singlet pairing, and can be interpreted with the equal-spin pairing state
with a large exchange field along the c axis, which was studied by Mineev
[Phys. Rev. B 81, 180504 (2010)].Comment: 5 pages, 4 figures, to be appear in PR
Universality and Critical Behavior at the Critical-End-Point on Itinerant-Metamagnet UCoAl
We performed nuclear-magnetic-resonance (NMR) measurements on
itinerant-electron metamagnet UCoAl in order to investigate the critical
behavior of the magnetism near a metamagnetic (MM) critical endpoint (CEP). We
derived c-axis magnetization and its fluctuation from the
measurements of Knight shift and nuclear spin-lattice relaxation rate
as a function of the c-axis external field () and temperature (). We
developed contour plots of and on the - phase diagram,
and observed the strong divergence of at the CEP. The critical exponents
of and near the CEP are estimated, and found to be close to the
universal properties of a three-dimensional (3-D) Ising model. We indicate that
the critical phenomena at the itinerant-electron MM CEP in UCoAl have a common
feature as a gas-liquid transition.Comment: 8 Pages, 14 figure
Nonreciprocal Phonon Propagation in a Metallic Chiral Magnet
The phonon magnetochiral effect (MChE) is the nonreciprocal acoustic and
thermal transports of phonons caused by the simultaneous breaking of the mirror
and time-reversal symmetries. So far, the phonon MChE has been observed only in
a ferrimagnetic insulator Cu2OSeO3, where the nonreciprocal response disappears
above the Curie temperature of 58 K. Here, we study the nonreciprocal acoustic
properties of a room-temperature ferromagnet Co9Zn9Mn2 for unveiling the phonon
MChE close to the room temperature. Surprisingly, the nonreciprocity in this
metallic compound is enhanced at higher temperatures and observed up to 250 K.
This clear contrast between insulating Cu2OSeO3 and metallic Co9Zn9Mn2 suggests
that metallic magnets have a mechanism to enhance the nonreciprocity at higher
temperatures. From the ultrasound and microwave-spectroscopy experiments, we
conclude that the magnitude of the phonon MChE of Co9Zn9Mn2 mostly depends on
the magnon bandwidth, which increases at low temperatures and hinders the
magnon-phonon hybridization. Our results suggest that the phonon nonreciprocity
could be further enhanced by engineering the magnon band of materials.Comment: 6 pages, 4 figures, 1 tabl
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