Magnetic heat transport in R_2CuO_4 with R = La, Pr, Nd, Sm, Eu, and Gd (original) (raw)
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In-Plane Thermal Conductivity ofNd2CuO4: Evidence for Magnon Heat Transport
Physical Review Letters, 2003
We report the temperature and magnetic field dependence of the in-plane thermal conductivity (ab) of high-quality monocrystalline Nd 2 CuO 4. Isothermal measurements of the field dependence of ab at low temperatures (2 K T 5 K) show no change in ab below a critical magnetic field H c (H c 4:5 T for H k 100) and H c 2:5 T for H k 110). Above H c , ab more than doubles as H is increased to 9 T. At H c , there is a transition from a noncollinear to a collinear arrangement of the Nd and Cu spins and a collapse of the gap, , in an acoustic magnon branch at k 0. Closure of this gap appears to allow the conduction of substantial amounts of heat by acoustic magnons.
Physical Review Letters, 2004
It was recently demonstrated that the anisotropic phonon heat transport behavior is a good probe of the stripe formation in La2−xSrxCuO4 (LSCO) [X. F. Sun et al., Phys. Rev. B 67, 104503 (2003)]. Using this probe, we examined an electron-doped cuprate Pr1.3−xLa0.7CexCuO4 (PLCCO) and found that essentially the same features as those in LSCO are observed. Moreover, the in-plane resistivity ρ ab of lightly-doped PLCCO shows metallic behavior (dρ ab /dT > 0) in the Néel ordered state with a mobility comparable to that in LSCO. It is discussed that these peculiar properties in common with LSCO signify the existence of stripes in electron-doped cuprates.
Anisotropic thermal conductivity of superconducting lanthanum cuprate
Physical review. B, Condensed matter, 1990
%'e have measured the thermal conductivity of a single crystal of Lal.96SrQ.Q4Cu04 in directions both parallel and perpendicular to the copper-oxygen planes. While the effects of electron scattering for in-plane heat transport are strong, the transfer of heat across the Cu02 planes is limited primarily by sheetlike faults with spacings on the order of 100 A. The resulting very high out-of-plane thermal resistivity masks the effects of electron scattering in this direction and prevents a careful study of the anisotropy of the electron-phonon coupling in this superconductor. We have undertaken the first study of the directional dependence of the thermal conductivity x of a hightemperature superconductor, in this case a lanthanum cuprate compound. Though members of this family have comparatively low transition temperatures (0-40 K, depending on Sr, Ba, or Ca doping content), they have proven to be the easiest to grow into the large single crystals required for these thermal measurements.
Spin-wave dispersion and transition temperature in the cuprate antiferromagnetLa2CuO4
Physical Review B, 2003
We have studied the spin-wave dispersion at low temperatures and the transition temperature (T N) of the spin-1 2 antiferromagnet and high-T C parent La 2 CuO 4. The values of the in-plane exchange parameters ͑including first, second, and third nearest neighbors͒ are determined by an accurate fit to the recently experimentally observed in-plane spin-wave spectrum, obtained by the high-resolution inelastic neutron scattering performed on La 2 CuO 4 ͓Phys. Rev. Lett. 86, 5377 ͑2001͔͒. The analysis of the Néel temperature shows that the in-plane spin anisotropy () is much more significant than the three dimensionality, since T N of the three-dimensional ͑3D͒-antiferromagnet depends rather weakly on the value of the interlayer coupling (Ќ). We obtain that the Néel temperature of the 3D-antiferromagnet varies only weakly within the very wide interval of Ќ and the Néel temperature of the anisotropic 2D (0, Ќ ϭ0) antiferromagnet does not differ from the 3D value for the same. These conclusions are valid for both tetragonal and orthorhombic structures. However, dependence of T N is essentially different: for ϭ0, T N of the tetragonal structure becomes 0, while T N of the orthorhombic structure remains finite. These results are valid within the frame of the Tyablikov approximation.
2007
This experimental work focusses on the magnetic thermal conductivity, κmag, of the one-dimensional two-leg spin ladder system Sr14Cu24O41 and the spin chain system SrCuO2. These two S = 1 2 antiferromagnetic Heisenberg compounds possess enormous magnetic contributions to the heat transport which in some cases exceed the phonon contributions by more than one order of magnitude. Despite of intense ongoing experimental and theoretical investigations, the underlying mechanism of the magnetic heat transport remains unclear. The study of κmag aims a better understanding of the basic physics which determine mobility, scattering and dissipation of the dispersing magnetic excitations. The most important tool used in this study is to selectively influence the structure and the electronic and magnetic properties of the compounds through doping. For this purpose single crystalline samples were produced using the Traveling Solvent Floating Zone technique, a crucible-free technology, which allows...
Heat transport in doped SrCuO2
Journal of Magnetism and Magnetic Materials, 2005
We report results on the heat transport in the spin chain system Sr 1Àx Ca x CuO 2 : The thermal conductivity in this compound is strongly anisotropic indicating excess thermal conductivity in the chain direction. Upon Ca-doping the thermal conductivity due to acoustic phonons is effectively suppressed, allowing a better qualitative and quantitative analysis of the excess thermal conductivity.