Anomalous broadening of the spin-flop transition in the reentrant spin-glass phase of La$_{2-x}$Sr$_x$CuO$_4$ ($x=0.018$)

Although La(2)Cu(1-x)Li(x)O(4) [Li-LCO] differs from La(2-x)Sr(x)CuO(4) [Sr-LCO] in many ways (e.g., the absence of metallic transport, high-Tc superconductivity, and incommensurate antiferromagnetic correlations), it has been known that certain magnetic properties are remarkably similar. The present work establishes the detailed bulk magnetic phase diagram of Li-LCO (0 <= x <= 0.07), which is found to be nearly identical to that of lightly-doped Sr-LCO, and therefore extends...

We report a comprehensive $^{139}$La and $^{63}$Cu nuclear magnetic resonance study on La$_{2-x}$Sr$_x$CuO$_4$ ($0.07\leq x \leq 0.2$) single crystals. The $^{139}$La spin-lattice relaxation rate $^{139}T_1^{-1}$ is drastically influenced by Sr doping $x$ at low temperatures. A detailed field dependence of $^{139}T_1^{-1}$ at $x=1/8$ suggests that charge ordering induces the critical slowing down of spin fluctuations toward glassy spin order and competes with superconductivit...

Using the experimental data given in Phys. Rev. B70, 220507 (2004), we show that -- unlike the effective coupling discussed in this paper -- the net average antiferromagnetic interlayer coupling in doped lanthanum cuprates depends only weakly on the doping or on the temperature. We argue that the effective coupling is proportional to the square of the staggered magnetization, and does not supply new information about the origin of the suppression of the magnetic order in dope...

Neutron scattering experiments reveal that a diagonal spin modulation, which is a one-dimensional modulation rotated away by 45$^\circ$ from that in the superconducting phase, occurs universally across the insulating spin-glass phase in La$_{2-x}$Sr$_x$CuO$_4$ (0.02$\le x\le$0.055). This establishes an intimate relation between the magnetism and the transport properties in the high-temperature copper oxide superconductors. Furthermore, it is found that the charge density per ...

The weak ferromagnetism present in insulating La_{2}CuO_4 at low doping leads to a spin flop transition, and to transverse (interplane) hopping of holes in a strong external magnetic field. This results in a dimensional crossover 2D $\to$ 3D for the in-plane transport, which in turn leads to an increase of the hole's localization length and increased conduction. We demonstrate theoretically that as a consequence of this mechanism, a frequency-dependent jump of the in-plane ac...

We study long wavelength magnetic excitations in lightly doped La_{2-x}Sr_{x}CuO_{4} (x < 0.03) detwinned crystals. The lowest energy magnetic anisotropy induced gap can be understood in terms of the antisymmetric spin interaction inside the antiferromagnetic (AF) phase. The second magnetic resonace, analyzed in terms of in-plane spin anisotropy, shows unconventional behavior within the AF state and led to the discovery of collective spin excitations pertaining to a field ind...

Transverse-field muon spin rotation measurements of overdoped La2-xSrxCuO4 reveal a large broadening of the local magnetic field distribution in response to applied field, persisting to high temperatures. The field-response is approximately Curie-Weiss like in temperature and is largest for the highest doping investigated. Such behaviour is contrary to the canonical Fermi-liquid picture commonly associated with the overdoped cuprates and implies extensive heterogeneity in thi...

A neutron scattering study of nonsuperconducting La$_{2-x}$Sr$_x$CaCu$_2$O$_6$ (x=0 and 0.2), a bilayer copper oxide without CuO chains, has revealed an unexpected tetragonal-to-orthorhombic transition with a doping dependent transition temperature. The predominant structural modification below the transition is an in-plane shift of the apical oxygen. In the doped sample, the orthorhombic superstructure is strongly disordered, and a glassy state involving both magnetic and st...

We present a single crystal Cu NMR study of the cuprate superconductor La$_{2-x}$Sr$_{x}$CuO$_4$ with hole doping levels between $x=2$\% and $8$\%. Measurements with short spin echo times enable us to systematically study the local properties of the electronic spin system in the region of the phase diagram where the material evolves from the insulating antiferromagnetic parent phase to the superconducting state. We find evidence for qualitative changes as the Sr concentration...

We examine the low-temperature magnetic properties of moderately doped LaSrCuO paying particular attention to the spin-glass (SG) phase and the C-IC transition as they are affected by Sr impurity disorder. New measurements of the low-temperature susceptibility in the SG phase show an increase of an anomalously small Curie constant with doping. This behaviour is explained in terms of our theoretical work that finds small clusters of AFM correlated regions separated by disorder...