Tuning competing orders in ${\text{La}}_{2-x}{\text{Sr}}_x{\text{CuO}}_4$ cuprate superconductors by the application of an external magnetic field

We report the results of a combined muon-spin rotation and neutron-scattering study on ${\text{La}}_{2-x}{\text{Sr}}_x{\text{CuO}}_4$ in the vicinity of the so-called 1/8 anomaly. Application of a magnetic field drives the system toward 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.

Figure 1

$Q$ scans around ${\mathbf{Q}}_{\text{IC}}$ performed on (a) $x=0.145$, (b) $x=0.105$, (c) $x=0.12$, and (d) LNSCO. Solid lines are Gaussian fits to the data. Note the different $x$-axis scales for the left and right panels. The magnetic correlation length $\xi$ is derived from the full width at half maximum (FWHM) of the magnetic peaks. Data in (c) and (d) are resolution limited. (e) $T$ dependences of the intensity at ${\mathbf{Q}}_{\text{IC}}$ for $x=0.105$, $x=0.12$, and LNSCO. Open symbols indicate data taken in ZF, while filled symbols represent data taken in a magnetic field. Lines are guides for the eye.

Figure 2

$\mu \text{SR}$ time spectra obtained in ZF and low temperatures. The solid lines are fits with a Bessel function for LNSCO and $x=0.12$, a simple exponential decay $\left(x=0.105\right)$, and a Kubo-Toyabe function $\left(x=0.145\right)$.

Figure 3

$H$ dependences of the response at ${\mathbf{Q}}_{\text{IC}}$ for LSCO $x=0.105$, $x=0.12$, $x=0.145$, and LNSCO. The solid lines are fits to $\mu =\sqrt{I\left(H\right)}\propto \sqrt{\left(H/H_c\right)\text{ln}\left(H_c/H\right)}$ (Ref. 33). Here the ZF moments estimated by $\mu \text{SR}$ are used and the gray colors indicate the error related to the determination of the ZF order moment. The $x=0.145$ data are presented in arbitrary units.

Figure 4

(Color) Schematic doping-field phase diagram for ${\text{La}}_{2-x}{\text{Sr}}_x{\text{CuO}}_4$. The ordered moment is given in false colors with red (blue) as the maximum (minimum).