59 research outputs found
Localized f electrons in CexLa1-xRhIn5: dHvA Measurements
Measurements of the de Haas-van Alphen effect in CexLa1-xRhIn5 reveal that
the Ce 4f electrons remain localized for all x, with the mass enhancement and
progressive loss of one spin from the de Haas-van Alphen signal resulting from
spin fluctuation effects. This behavior may be typical of antiferromagnetic
heavy fermion compounds, inspite of the fact that the 4f electron localization
in CeRhIn5 is driven, in part, by a spin-density wave instability.Comment: 4 pages, 4 figures, submitted to PR
Heat capacity studies of Ce and Rh site substitution in the heavy fermion antiferromagnet CeRhIn_5;: Short-range magnetic interactions and non-Fermi-liquid behavior
In heavy fermion materials superconductivity tends to appear when long range
magnetic order is suppressed by chemical doping or applying pressure. Here we
report heat capacity measurements on diluted alloyes of the heavy fermion
superconductor CeRhIn_5;. Heat capacity measurements have been performed on
CeRh_{1-y}Ir_{y}In_5; (y <= 0.10) and Ce_{1-x}La_{x}Rh_{1-y}Ir_{y}In_5; (x <=
0.50) in applied fields up to 90 kOe to study the affect of doping and magnetic
field on the magnetic ground state. The magnetic phase diagram of
CeRh_{0.9}Ir_{0.1}In_5; is consistent with the magnetic structure of CeRhIn_5;
being unchanged by Ir doping. Doping of Ir in small concentrations is shown to
slightly increase the antiferromagnetic transition temperature T_{N} (T_{N}=3.8
K in the undoped sample). La doping which causes disorder on the Ce sublattice
is shown to lower T_{N} with no long range order observed above 0.34 K for
Ce_{0.50}La_{0.50}RhIn_5;. Measurements on Ce_{0.50}La_{0.50}RhIn_5; show a
coexistence of short range magnetic order and non-Fermi-liquid behavior. This
dual nature of the Ce 4f-electrons is very similar to the observed results on
CeRhIn_5; when long range magnetic order is suppressed at high pressure.Comment: 8 pages, 9 figure
Field-induced magnetic transitions in the quasi-two-dimensional heavy-fermion antiferromagnets Ce_{n}RhIn_{3n+2} (n=1 or 2)
We have measured the field-dependent heat capacity in the tetragonal
antiferromagnets CeRhIn and CeRhIn, both of which have an
enhanced value of the electronic specific heat coefficient
mJ/mol-Ce K above . For the specific heat data at zero
applied magnetic field are consistent with the existence of an anisotropic
spin-density wave opening a gap in the Fermi surface for CeRhIn while
CeRhIn shows behavior consistent with a simple antiferromagnetic
magnon. From these results, the magnetic structure, in a manner similar to the
crystal structure, appears more two-dimensional in CeRhIn than in
CeRhIn where only about 12% of the Fermi surface remains ungapped
relative to 92% for CeRhIn. When both compounds behave in a
manner expected for heavy fermion systems as both and the electronic
heat capacity decrease as field is applied. When the field is applied in the
tetragonal basal plane (), CeRhIn and CeRhIn have very
similar phase diagrams which contain both first- and second-order field-induced
magnetic transitions .Comment: 15 pages, 4 figure
Unusual giant magnetostriction in the ferrimagnet GdCaMnO
We report an unusual giant linear magnetostrictive effect in the ferrimagnet
GdCaMnO (80 K). Remarkably, the
magnetostriction, negative at high temperature (), becomes
positive below 15 K when the magnetization of the Gd sublattice overcomes the
magnetization of the Mn sublattice. A rather simple model where the magnetic
energy competes against the elastic energy gives a good account of the observed
results and confirms that Gd plays a crucial role in this unusual observation.
Unlike previous works in manganites where only striction associated with 3
Mn orbitals is considered, our results show that the lanthanide 4 orbitals
related striction can be very important too and it cannot be disregarded.Comment: 6 pages, 3 figure
Pressure Induced Change in the Magnetic Modulation of CeRhIn5
We report the results of a high pressure neutron diffraction study of the
heavy fermion compound CeRhIn5 down to 1.8 K. CeRhIn5 is known to order
magnetically below 3.8 K with an incommensurate structure. The application of
hydrostatic pressure up to 8.6 kbar produces no change in the magnetic wave
vector qm. At 10 kbar of pressure however, a sudden change in the magnetic
structure occurs. Although the magnetic transition temperature remains the
same, qm increases from (0.5, 0.5, 0.298) to (0.5, 0.5, 0.396). This change in
the magnetic modulation may be the outcome of a change in the electronic
character of this material at 10 kbar.Comment: 4 pages, 3 figures include
Comment on "Short-range magnetic interactions in the spin-ice compound Ho2Ti2O7"
In their recent communication (Phys. Rev. B 64, 060406(R) (2001)) Cornelius
and Gardner have reported the results of magnetization and susceptibility
studies on single crystals of the pyrochlore Ho2Ti2O7. The observed field
dependence of magnetization is totally unexpected, as it seems to suggest that
the magnetic moments in this compound do not obey the 'ice-rule'. We have
re-measured the magnetization curves for Ho2Ti2O7 single crystal for the three
principal directions of an applied magnetic field and found nearly perfect
agreement with the predictions for a nearest-neighbor spin-ice model.Comment: comment on Phys. Rev. B 64, 060406(R) (2001
Pressure-Temperature Phase Diagram of Antiferromagnetism and Superconductivity in CeRhIn5 and CeIn3 : In-NQR Study under Pressure
We report the novel pressure() - temperature() phase diagram of
antiferromagnetism and superconductivity in CeRhIn and CeIn revealed by
the In nuclear-spin-lattice-relaxation () measurement. In the
itinerant magnet CeRhIn, we found that the N\'eel temperature is
reduced at 1.23 GPa with an emergent pseudogap behavior. In CeIn,
the localized magnetic character is robust against the application of pressure
up to 1.9 GPa, beyond which the system evolves into an itinerant
regime in which the resistive superconducting phase emerges. We discuss the
relationship between the phase diagram and the magnetic fluctuations.Comment: 4 pages, 3 figures, to be published in Phys.Rev.B. Rapid
Mass-Enhanced Fermi Liquid Ground State in NaCoO
Magnetic, transport, and specific heat measurements have been performed on
layered metallic oxide NaCoO as a function of temperature .
Below a characteristic temperature =3040 K, electrical resistivity
shows a metallic conductivity with a behavior and magnetic susceptibility
deviates from the Curie-Weiss behavior showing a broad peak at 14 K. The
electronic specific heat coefficient is 60 mJ/molK at 2 K.
No evidence for magnetic ordering is found. These behaviors suggest the
formation of mass-enhanced Fermi liquid ground state analogous to that in
-electron heavy fermion compound LiVO.Comment: 4 pages, 4 figures, to be published in Phys. Rev. B 69 (2004
Anisotropic three-dimentional magnetic fluctuations in heavy fermion CeRhIn5
CeRhIn5 is a heavy fermion antiferromagnet that orders at 3.8 K. The
observation of pressure-induced superconductivity in CeRhIn5 at a very high Tc
of 2.1 K for heavy fermion materials has led to speculations regarding to its
magnetic fluctuation spectrum. Using magnetic neutron scattering, we report
anisotropic three-dimensional antiferromagnetic fluctuations with an energy
scale of less than 1.7 meV for temperatures as high as 3Tc. In addition, the
effect of the magnetic fluctuations on electrical resistivity is well described
by the Born approximation.Comment: 4 pages, 4 figure
Interplay among critical temperature, hole content, and pressure in the cuprate superconductors
Within a BCS-type mean-field approach to the extended Hubbard model, a
nontrivial dependence of T_c on the hole content per unit CuO_2 is recovered,
in good agreement with the celebrated non-monotonic universal behaviour at
normal pressure. Evaluation of T_c at higher pressures is then made possible by
the introduction of an explicit dependence of the tight-binding band and of the
carrier concentration on pressure P. Comparison with the known experimental
data for underdoped Bi2212 allows to single out an `intrinsic' contribution to
d T_c / d P from that due to the carrier concentration, and provides a
remarkable estimate of the dependence of the inter-site coupling strength on
the lattice scale.Comment: REVTeX 8 pages, including 5 embedded PostScript figures; other
required macros included; to be published in Phys. Rev. B (vol. 54
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