195 research outputs found
Aspek Hukum Dan Tanggung Jawab Pers
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Low energy magnetic excitation spectrum of the unconventional ferromagnet CeRhB
The magnetic excitation spectrum of the unconventional ferromagnet
CeRhB was measured by inelastic neutron scattering on single
crystal sample in the magnetically ordered and paramagnetic phases. The
spin-wave excitation spectrum evidences high exchange interaction along the
c-axis about two orders of magnitude higher than the ones in the basal plane of
the hexagonal structure. Both strong out of plane and small in plane
anisotropies are found. This latter point confirms that considering the =5/2
multiplet alone is not adequate for describing the ground state of
CeRhB. Quasielastic scattering measured above is also
strongly anisotropic between the basal plane and the c-axis and suggests
localized magnetism.Comment: 8 Figure
Spin fluctuations probed by NMR in paramagnetic spinel LiVO: a self-consistent renormalization theory
Low frequency spin fluctuation dynamics in paramagnetic spinel LiVO,
a rare 3-electron heavy fermion system, is investigated. A parametrized
self-consistent renormalization (SCR) theory of the dominant AFM spin
fluctuations is developed and applied to describe temperature and pressure
dependences of the low- nuclear spin-lattice relaxation rate in this
material. The experimental data for available down to K are
well reproduced by the SCR theory, showing the development of AFM spin
fluctuations as the paramagnetic metal approaches a magnetic instability under
the applied pressure. The low- upturn of detected below 0.6 K under
the highest applied pressure of 4.74 GPa is explained as the nuclear spin
relaxation effect due to the spin freezing of magnetic defects unavoidably
present in the measured sample of LiVO.Comment: 11 pages, 2 figure
Non-Fermi-liquid behavior in Ce(RuFe)Ge: cause and effect
We present inelastic neutron scattering measurements on the intermetallic
compounds Ce(RuFe)Ge (=0.65, 0.76 and 0.87). These
compounds represent samples in a magnetically ordered phase, at a quantum
critical point and in the heavy-fermion phase, respectively. We show that at
high temperatures the three compositions have the identical response of a local
moment system. However, at low temperatures the spin fluctuations in the
critical composition are given by non-Fermi-liquid dynamics, while the spin
fluctuations in the heavy fermion system show a simple exponential decay in
time. In both compositions, the lifetime of the fluctuations is determined
solely by the distance to the quantum critical point. We discuss the
implications of these observations regarding the possible origins of
non-Fermi-liquid behavior in this system.Comment: 4 figures, submitted to PR
Magnetic Fluctuations and Correlations in MnSi - Evidence for a Skyrmion Spin Liquid Phase
We present a comprehensive analysis of high resolution neutron scattering
data involving Neutron Spin Echo spectroscopy and Spherical Polarimetry which
confirm the first order nature of the helical transition and reveal the
existence of a new spin liquid skyrmion phase. Similar to the blue phases of
liquid crystals this phase appears in a very narrow temperature range between
the low temperature helical and the high temperature paramagnetic phases.Comment: 11 pages, 16 figure
Electronic states and magnetic excitations in LiV2O4: Exact diagonalization study
Motivated by recent inelastic neutron scattering experiment we examine
magnetic properties of LiV2O4. We consider a model which describes the
half-filled localized A1g spins interacting via frustrated antiferromagnetic
Heisenberg exchange and coupled by local Hund's interaction with the 1/8-filled
itinerant Eg band, and study it within an exact diagonalization scheme. In the
present study we limited the analysis to the case of the cluster of two
isolated tetrahedrons. We obtained that both the ground state structure and
low-lying excitations depend strongly on the value of the Hund's coupling which
favors the triplet states. With increasing temperature the triplet states
become more and more populated which results in the formation of non-zero
residual magnetic moment. We present the temperature dependence of calculated
magnetic moment and of the spin-spin correlation functions at different values
of Hund's coupling and compare them with the experimental results.Comment: 7 pages. 6 eps figure
Magnetic field resistant quantum interferences in bismuth nanowires based Josephson junctions
We investigate proximity induced superconductivity in micrometer-long bismuth
nanowires con- nected to superconducting electrodes with a high critical field.
At low temperature we measure a supercurrent that persists in magnetic fields
as high as the critical field of the electrodes (above 11 T). The critical
current is also strongly modulated by the magnetic field. In certain samples we
find regular, rapid SQUID-like periodic oscillations occurring up to high
fields. Other samples ex- hibit less periodic but full modulations of the
critical current on Tesla field scales, with field-caused extinctions of the
supercurrent. These findings indicate the existence of low dimensionally, phase
coherent, interfering conducting regions through the samples, with a subtle
interplay between orbital and spin contributions. We relate these surprising
results to the electronic properties of the surface states of bismuth, strong
Rashba spin-orbit coupling, large effective g factors, and their effect on the
induced superconducting correlations.Comment: 5 page
MicroRNA expression profiling of porcine mammary epithelial cells after challenge with Escherichia coli in vitro
Background Coliform mastitis is a symptom of postpartum dysgalactia syndrome
(PDS), a multifactorial infectious disease of sows. Our previous study showed
gene expression profile change after bacterial challenge of porcine mammary
epithelial cells (PMECs). These mRNA expression changes may be regulated
through microRNAs (miRNAs) which play critical roles in biological processes.
Therefore, miRNA expression profile was investigated in PMECs. Results PMECs
were isolated from three lactating sows and challenged with heat-inactivated
potential mastitis-causing pathogen Escherichia coli (E. coli) for 3 h and 24
h, in vitro. At 3 h post-challenge with E. coli, target gene prediction
identified a critical role of miRNAs in regulation of host immune responses
and homeostasis of PMECs mediated by affecting pathways including cytokine
binding (miR-202, miR-3277, miR-4903); IL-10/PPAR signaling (miR-3277,
miR-4317, miR-548); and NF-ĸB/TNFR2 signaling (miR-202, miR-2262, miR-885-3p).
Target genes of miRNAs in PMECs at 24 h were significantly enriched in
pathways associated with interferon signaling (miR-210, miR-23a, miR-1736) and
protein ubiquitination (miR-125, miR-128, miR-1280). Conclusions This study
provides first large-scale miRNA expression profiles and their predicted
target genes in PMECs after contact with a potential mastitis-causing E. coli
strain. Both, highly conserved miRNAs known from other species as well as
novel miRNAs were identified in PMECs, representing candidate predictive
biomarkers for PDS. Time-dependent pathogen clearance suggests an important
role of PMECs in inflammatory response of the first cellular barrier of the
porcine mammary gland
Muon spin rotation and neutron scattering study of the non-centrosymmetric tetragonal compound CeAuAl3
We have investigated the non-centrosymmetric tetragonal heavy-fermion
compound CeAuAl3 using muon spin rotation (muSR), neutron diffraction (ND) and
inelastic neutron scattering (INS) measurements. We have also revisited the
magnetic, transport and thermal properties. The magnetic susceptibility reveals
an antiferromagnetic transition at 1.1 K with a possibility of another magnetic
transition near 0.18 K. The heat capacity shows a sharp lambda-type anomaly at
1.1 K in zero-filed, which broadens and moves to higher temperature in applied
magnetic field. Our zero-field muSR and ND measurements confirm the existence
of a long-range magnetic ground state below 1.2 K. Further the ND study reveals
an incommensurate magnetic ordering with a magnetic propagation vector k = (0,
0, 0.52) and a spiral structure of Ce moments coupled ferromagnetically within
the ab-plane. Our INS study reveals the presence of two well-defined crystal
electric field (CEF) excitations at 5.1 meV and 24.6 meV in the paramagnetic
phase of CeAuAl3 which can be explained on the basis of the CEF theory.
Furthermore, low energy quasi-elastic excitations show a Gaussian line shape
below 30 K compared to a Lorentzian line shape above 30 K, indicating a
slowdown of spin fluctuation below 30 K. We have estimated a Kondo temperature
of TK=3.5 K from the quasi-elastic linewidth, which is in good agreement with
that estimated from the heat capacity. This study also indicates the absence of
any CEF-phonon coupling unlike that observed in isostructural CeCuAl3. The CEF
parameters, energy level scheme and their wave functions obtained from the
analysis of INS data explain satisfactorily the single crystal susceptibility
in the presence of two-ion anisotropic exchange interaction in CeAuAl3.Comment: 28 pages and 17 figure
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