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

We report the results of a combined muon spin rotation and neutron scattering study on La2-xSrxCuO4 in the vicinity of the so-called 1/8-anomaly. Application of a magnetic field drives the system towards a magnetically ordered spin-density-wave state, which is fully developed at 1/8 doping. The results are discussed in terms of competition between antiferromagnetic and superconducting order parameters.

In an effort to elucidate the origin of the Curie-like paramagnetism that is generic for heavily-overdoped cuprates, we have performed high transverse-field muon spin rotation (TF-muSR) measurements of La2-xSrxCuO4 single crystals over the Sr content range 0.145 < x < 0.33. We show that the x-dependence of the previously observed field-induced broadening of the internal magnetic field distribution above the superconducting transition temperature Tc reflects the presence of tw...

We have performed muon spin relaxation and low field ac-susceptibility measurements in a series of high quality samples of La_{2-x}Sr_xCuO_4 (x=0.08-0.24) as a function of temperature. Superconductivity is found to coexist with low temperature spin glass order up to the optimally doped region where the normal state pseudogap also closes. The systematic depletion of the superfluid density with the enhancement of aniferromagnetic correlations with underdoping indicates a compet...

We performed systematic measurements of magnetic susceptibility on single crystals of La$_{1.875}$Ba$_{0.125-x}$Sr$_x$CuO$_4$. The dependence of the superconducting transition temperature on Sr-concentration demonstrates a step-like pattern upon doping at {\it x}$\sim$0.08 as the crystal structure changes from low-temperature tetragonal (LTT) to low-temperature orthorhombic (LTO) phase at low temperature. Upon cooling, an anomalous upturn in the susceptibility was observed at...

The ESR signal of Gd spin probes (0.5 at %) as well as the static normal state susceptibility of Eu (J(Eu^{3+})=0) doped La_{2-x-y}Sr_xEu_yCuO_4 reveal pronounced changes of the Cu magnetism at the structural transition from the orthorhombic to the low temperature tetragonal phase for all non-superconducting compositions. Both a jumplike decrease of \chi as well as the ESR data show an increase of the in-plane magnetic correlation length in the LTT phase. From the Gd^{3+} ESR...

Magnetic-field-induced ordering of electrons around vortices is a striking phenomenon recently found in high-$T_c$ cuprates. To identify its consequence in the quasiparticle dynamics, the magnetic-field ($H$) dependence of the low-temperature thermal conductivity $\kappa$ of La$_{2-x}$Sr$_x$CuO$_4$ crystals is studied for a wide doping range. It is found that the behavior of $\kappa(H)$ in the sub-Kelvin region changes drastically across optimum doping, and the data for under...

The in-plane magnetoresistance (MR) of a single crystal La_{1.97}Sr_{0.03}CuO_{4} has been studied at low temperatures T using several experimental protocols. At T well below the spin-glass transition temperature, the MR becomes positive and exhibits several glassy features, such as history dependence, memory and hysteresis. These observations are qualitatively similar to the previously reported behavior of the out-of-plane resistance. The results suggest that the memory effe...

We have studied the interlayer coupling in the antiferromagnetic (AF) phase of Sr and Zn doped La2CuO4 by analyzing the spin flip transition in the magnetization curves. We find that the interlayer coupling strongly depends on the mobility of the hole charge carriers. Samples with the same hole content as well as the same Neel temperature but a different hole mobility, which we adjusted by Zn co-doping, can have a very different interlayer coupling. Our results suggest that o...

The effects of nonmagnetic Zn and magnetic Ni substitution for Cu site on magnetism are studied by measurements of uniform magnetic susceptibility for lightly doped La_{2-x}Sr_xCu_{1-z}M_zO_4 (M=Zn or Ni) polycrystalline samples. For the parent x=0, Zn doping suppresses the N\'{e}el temperature T_N whereas Ni doping hardly changes T_N up to z=0.3. For the lightly doped samples with T_N~0, the Ni doping recovers T_N. For the superconducting samples, the Ni doping induces the s...

In order to investigate the relationship between the so-called stripe correlations and the high-Tc superconductivity, we have carried out magnetic susceptibility and zero-field muon-spin-relaxation measurements in partially Fe-substituted La2-xSrxCu1-yFeyO4 (LSCFO). It has been found that the Fe substitution induces successive magnetic transitions in the overdoped regime, namely, a spin-glass transition of Fe3+ spins due to the RKKY interaction based on itinerant spins at hig...