Stripe order of ${\mathrm{La}}_{1.64}{\mathrm{Eu}}_{0.2}{\mathrm{Sr}}_{0.16}{\mathrm{CuO}}_4$ in magnetic fields studied by resonant soft x-ray scattering

We present results on the magnetic field dependence of the stripe order in ${\mathrm{La}}_{1.64}{\mathrm{Eu}}_{0.2}{\mathrm{Sr}}_{0.16}{\mathrm{CuO}}_4$ (LESCO). Using resonant soft x-ray scattering at the oxygen $K$ edge to probe the (0.259,0,0.648) superlattice reflection, which is commonly associated to charge stripes, we found no pronounced difference in the wave vector, peak widths, and integrated intensity for magnetic fields up to $B=6$ T. This is in strong contrast to the behavior observed for ${\mathrm{La}}_{1.875}{\mathrm{Sr}}_{0.125}{\mathrm{CuO}}_4$, where a stabilization of the charge modulation in high magnetic fields has been demonstrated.

Figure 1

(a) Experimental setup for RSXS and XAS experiments. (b) XAS total yield spectrum of LESCO near the O K absorption edge at $T=52.5$ K. (c) Intensity of a $2\mathrm{\Theta }$ RSXS scan for $B=0$ T, $T=5$ K around the $(h,0,l)=(0.259,0,0.648)$ superlattice reflection. On the $x$ axis, the in-plane component h of the x-ray scattering vector is shown. The x-ray intensity is shown in red, the Lorentzian fit according to Eq. (1) is shown in green, and the background is shown in blue.

Figure 2

RSXS (red bars) and Lorentzian fits on the electronic order peak for $B=6$ (a) and 0 T (b). For each scan, $\alpha , k, s$, and $h_0$ from Eq. (1) were free fit parameters. $\beta$ and $\gamma$ were assumed to depend on the magnetic field, but not on temperature and taken from the RSXS scans at $T=60$ K. For $T>42.5$ K, reliable fits of the RSXS could not be achieved due to the strong correlation of fit parameters. The data for 62.5 K (60 K) were thus fitted with $k$ in Eq. (1) set to zero. For $B=6$ T (a), the RSXS signal of three consecutive, identical scans was summed up to achieve superior statistics, while for $B=0$ T, the RSXS was only measured once for each temperature.

Figure 3

(a) Peak width $s$ from Lorentzian fits of the RSXS in Fig. 2. The electronic order peak is broader when a magnetic field is applied. The weak variation of the peak width with temperature is similar for both cases. (b) Integrated intensity of the electronic order peak at $B=0$ (red) and 6 T (green), taken from Lorentzian fits with Eq. (1). The electronic order peak is more intense in a magnetic field and the transition temperature $T_{\mathrm{CO}}$ is increased.

Figure 4

Selected RSXS and Lorentzian fits on the electronic order peak for $B=6$ and 0 T. Only the Lorentzian contribution from Eq. (1) is shown, while the background was subtracted from fits and experimental data. For each scan, $\alpha , k, s$, and $h_0$ from Eq. (1) were free fit parameters. $\beta$ and $\gamma$ were assumed to depend on the magnetic field, but not on temperature and taken from the RSXS scans at $T=60$ K. For $B=6$ T, the RSXS signal of three consecutive, identical scans was summed up to achieve superior statistics, while for $B=0$ T, the RSXS was only measured once for each temperature. Blue dotted lines are a guide to the eye for the $B=6$ T maximum intensity. For all measured temperatures, the superlattice peaks at 6 T are slightly more intense as compared to zero field.