4,649 research outputs found
Ferromagnetism Induced by Uniaxial Pressure in the Itinerant Metamagnet Sr3Ru2O7
We report a uniaxial-pressure study on the magnetisation of single crystals
of the bilayer perovskite Sr3Ru2O7, a metamagnet close to a ferromagnetic
instability. We observed that the application of a uniaxial pressure parallel
to the c-axis induces ferromagnetic ordering with a Curie temperature of about
80 K and critical pressures of about 4 kbar or higher. This value for the
critical pressure is even higher than the value previously reported (~ 1 kbar),
which might be attributed to the difference of the impurity level. Below the
critical pressure parallel to the c-axis, the metamagnetic field appears to
hardly change. We have also found that uniaxial pressures perpendicular to the
c-axis, in contrast, do not induce ferromagnetism, but shift the metamagnetic
field to higher fields.Comment: Accepted for publication in Proc of 24th Int. Conf. on Low
Temperature Physics (LT24); 2 page
Symmetry-breaking lattice distortion in Sr_3Ru_2O_7
The electronic nematic phase of SrRuO is investigated by
high-resolution in-plane thermal expansion measurements in magnetic fields
close to 8 T applied at various angles off the c-axis. At
we observe a very small () lattice distortion which
breaks the four-fold in-plane symmetry, resulting in nematic domains with
interchanged - and b-axis. At the domains are
almost fully aligned and thermal expansion indicates an area-preserving lattice
distortion of order which is likely related to orbital
ordering. Since the system is located in the immediate vicinity to a
metamagnetic quantum critical end point, the results represent the first
observation of a structural relaxation driven by quantum criticality.Comment: 4 pages, 5 figures, PRL accepte
Electronic nematicity and its relation to quantum criticality in Sr_3Ru_2O_7 studied by thermal expansion
We report high-resolution measurements of the in-plane thermal expansion
anisotropy in the vicinity of the electronic nematic phase in SrRuO
down to very low temperatures and in varying magnetic field orientation. For
fields applied along the c-direction, a clear second-order phase transition is
found at the nematic phase, with critical behavior compatible with the
two-dimensional Ising universality class (although this is not fully
conclusive). Measurements in a slightly tilted magnetic field reveal a broken
four-fold in-plane rotational symmetry, not only within the nematic phase, but
extending towards slightly larger fields. We also analyze the universal scaling
behavior expected for a metamagnetic quantum critical point, which is realized
outside the nematic region. The contours of the magnetostriction suggest a
relation between quantum criticality and the nematic phase.Comment: 8 pages, 12 Figures, invited paper at QCNP 2012 conferenc
Anisotropy of the low-temperature magnetostriction of Sr3Ru2O7
We use high-resolution capacitive dilatometry to study the low-temperature
linear magnetostriction of the bilayer ruthenate SrRuO as a
function of magnetic field applied perpendicular to the ruthenium-oxide planes
(). The relative length change is detected either
parallel or perpendicular to the c-axis close to the metamagnetic region near
B=8 T. In both cases, clear peaks in the coefficient at three subsequent metamagnetic transitions are observed. For , the third transition at 8.1 T bifurcates at temperatures below 0.5
K. This is ascribed to the effect of an in-plane uniaxial pressure of about 15
bar, unavoidable in the dilatometer, which breaks the original fourfold
in-plane symmetry.Comment: 3 pages, 3 Figures, Manuscript for Proceedings of the International
Conference on Quantum Criticality and Novel Phases (QCNP09, Dresden
Orbital-selective Mass Enhancements in Multi-band CaSrRuO Systems Analyzed by the Extended Drude Model
We investigated optical spectra of quasi-two-dimensional multi-band CaSrRuO systems. The extended Drude model analysis on the
ab-plane optical conductivity spectra indicates that the effective mass should
be enhanced near . Based on the sum rule argument, we showed that the
orbital-selective Mott-gap opening for the bands, the widely
investigated picture, could not be the origin of the mass enhancement. We
exploited the multi-band effects in the extended Drude model analysis, and
demonstrated that the intriguing heavy mass state near should come from
the renormalization of the band.Comment: 4 figure
Mechanism of hopping transport in disordered Mott insulators
By using a combination of detailed experimental studies and simple
theoretical arguments, we identify a novel mechanism characterizing the hopping
transport in the Mott insulating phase of CaSrRuO near the
metal-insulator transition. The hopping exponent shows a systematic
evolution from a value of deeper in the insulator to the
conventional Mott value closer to the transition. This behavior,
which we argue to be a universal feature of disordered Mott systems close to
the metal-insulator transition, is shown to reflect the gradual emergence of
disorder-induced localized electronic states populating the Mott-Hubbard gap.Comment: 5 pages, 3 figures, To be published in Physical Review Letter
Detailed Topography of the Fermi Surface of Sr2RuO4
We apply a novel analysis of the field and angle dependence of the
quantum-oscillatory amplitudes in the unconventional superconductor Sr2RuO4 to
map its Fermi surface in unprecedented detail, and to obtain previously
inaccessible information on the band dispersion. The three quasi-2D Fermi
surface sheets not only exhibit very diverse magnitudes of warping, but also
entirely different dominant warping symmetries. We use the data to reassess
recent results on c-axis transport phenomena.Comment: REVTeX, 4 page
Pressure-Tuned Collapse of the Mott-Like State in Ca_{n+1}Ru_nO_{3n+1} (n=1,2): Raman Spectroscopic Studies
We report a Raman scattering study of the pressure-induced collapse of the
Mott-like phases of Ca_3Ru_2O_7 (T_N=56 K) and Ca_2RuO_4 (T_N=110 K). The
pressure-dependence of the phonon and two-magnon excitations in these materials
indicate: (i) a pressure-induced collapse of the antiferromagnetic (AF)
insulating phase above P* ~ 55 kbar in Ca_3Ru_2O_7 and P* ~ 5-10 kbar in
Ca_2RuO_4, reflecting the importance of Ru-O octahedral distortions in
stabilizing the AF insulating phase; and (ii) evidence for persistent AF
correlations above the critical pressure of Ca_2RuO_4, suggestive of phase
separation involving AF insulator and ferromagnetic metal phases.Comment: 3 figure
Multiple first-order metamagnetic transitions and quantum oscillations in ultrapure
We present measurements on ultra clean single crystals of the bilayered
ruthenate metal Sr3Ru2O7, which has a magnetic-field-tuned quantum critical
point. Quantum oscillations of differing frequencies can be seen in the
resistivity both below and above its metamagnetic transition. This frequency
shift corresponds to a small change in the Fermi surface volume that is
qualitatively consistent with the small moment change in the magnetisation
across the metamagnetic transition. Very near the metamagnetic field, unusual
behaviour is seen. There is a strong enhancement of the resistivity in a narrow
field window, with a minimum in the resistivity as a function of temperature
below 1 K that becomes more pronounced as the disorder level decreases. The
region of anomalous behaviour is bounded at low temperatures by two first-order
phase transitions. The implications of the results are discussed. PACS:
68.35.Rh, 71.27.+a, 72.15.-v, 74.70.PqComment: 12 pages 4 figures, submitte
Cyclotron Resonance in the Layered Perovskite Superconductor Sr2RuO4
We have measured the cyclotron masses in Sr2RuO4 through the observation of
periodic-orbit-resonances - a magnetic resonance technique closely related to
cyclotron resonance. We obtain values for the alpha, beta and gamma Fermi
surfaces of (4.33+/-0.05)me, (5.81+/-0.03)me and (9.71+/-0.11)me respectively.
The appreciable differences between these results and those obtained from de
Haas- van Alphen measurements are attributable to strong electron-electron
interactions in this system. Our findings appear to be consistent with
predictions for a strongly interacting Fermi liquid; indeed, semi-quantitative
agreement is obtained for the electron pockets beta and gamma.Comment: 4 pages + 3 figure
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