277 research outputs found
Artificial scaling laws of the dynamical magnetic susceptibility in heavy-fermion systems
We report here how artificial, thus erroneous, scaling laws of the dynamical
magnetic susceptibility can be obtained when data are not treated carefully. We
consider the example of the heavy-fermion system
CeLaRuSi and we explain how different kinds of
artificial scaling laws in can be plotted in a low temperature
regime where the dynamical susceptibility is nearly temperature independent.Comment: 4 pages, 4 figure
High-field irreversible moment reorientation in the antiferromagnet FeTe
Magnetization measurements have been performed on single-crystalline
FeTe in pulsed magnetic fields up to 53 T
and temperatures from 4.2 to 65 K. At K, a non-reversible reorientation
of the antiferromagnetic moments is observed at T as the pulsed
field is on the rise. No anomaly is observed at during the fall of the
field and, as long as the temperature is unchanged, during both rises and falls
of additional field pulses. The transition at is reactivated if the
sample is warmed up above the N\'{e}el temperature K and cooled
down again. The magnetic field-temperature phase diagram of FeTe in
is also investigated. We present the temperature
dependence of , as well as that of the antiferromagnetic-to-paramagnetic
borderline in temperatures above 40 K.Comment: 5 pages, 4 figure
Low energy spin fluctuations in the heavy fermion compound CeLaRuSi
We report inelastic neutron scattering measurements performed on a single
crystal of the heavy fermion compound CeLaRuSi,
which is at the borderline between an antiferromagnetically ordered and a
paramagnetic ground state. Intensity maps as a function of wavevector and
energy ( meV) were obtained at temperatures and 2 K, using
the time-of-flight spectrometer IRIS. An unexpected saturation of the
relaxation rate and static susceptibility of the spin fluctuations is found at
low temperatures.Comment: 2 pages, 2 figures, SCES'04 Proceeding
Further analysis of the quantum critical point of CeLaRuSi
New data on the spin dynamics and the magnetic order of
CeLaRuSi are presented. The importance of the Kondo
effect at the quantum critical point of this system is emphasized from the
behaviour of the relaxation rate at high temperature and from the variation of
the ordered moment with respect to the one of the N\'eel temperature for
various .Comment: Contribution for the Festschrift on the occasion of Hilbert von
Loehneysen 60 th birthday. To be published as a special issue in the Journal
of Low Temperature Physic
Antiferromagnetism and hot spots in CeIn
Enormous mass enhancement at ''hot spots'' on the Fermi surface (FS) of
CeIn has been reported at strong magnetic field near its antiferromagnetic
(AFM) quantum critical point [T. Ebihara et al., Phys. Rev. Lett. 93, 246401
(2004)] and ascribed to anomalous spin fluctuations at these spots. The ''hot
spots'' lie at the positions on FS where in non-magnetic LaIn the narrow
necks are protruded. In paramagnetic phase CeIn has similar spectrum. We
show that in the presence of AFM ordering its FS undergoes a topological change
at the onset of AFM order that truncates the necks at the ''hot spots'' for one
of the branches. Applied field leads to the logarithmic divergence of the dHvA
effective mass when the electron trajectory passes near or through the neck
positions. This effect explains the observed dHvA mass enhancement at the ''hot
spots'' and leads to interesting predictions concerning the spin-dependence of
the effective electron mass. The (T,B)-phase diagram of CeIn, constructed
in terms of the Landau functional, is in agreement with experiment.Comment: 4 pages, 1 figur
Ferromagnetism and Lattice Distortions in the Perovskite YTiO
The thermodynamic properties of the ferromagnetic perovskite YTiO are
investigated by thermal expansion, magnetostriction, specific heat, and
magnetization measurements. The low-temperature spin-wave contribution to the
specific heat, as well as an Arrott plot of the magnetization in the vicinity
of the Curie temperature K, are consistent with a
three-dimensional Heisenberg model of ferromagnetism. However, a magnetic
contribution to the thermal expansion persists well above , which
contrasts with typical three-dimensional Heisenberg ferromagnets, as shown by a
comparison with the corresponding model system EuS. The pressure dependences of
and of the spontaneous moment are extracted using thermodynamic
relationships. They indicate that ferromagnetism is strengthened by uniaxial
pressures and is weakened by uniaxial
pressures and hydrostatic pressure.
Our results show that the distortion along the - and -axes is further
increased by the magnetic transition, confirming that ferromagnetism is favored
by a large GdFeO-type distortion. The c-axis results however do not fit
into this simple picture, which may be explained by an additional
magnetoelastic effect, possibly related to a Jahn-Teller distortion.Comment: 12 pages, 13 figure
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