Suppression of antiferromagnetic order and orthorhombic distortion in superconducting $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$

Neutron-diffraction and high-resolution x-ray diffraction studies find that, similar to the closely related underdoped $\text{Ba}{\left({\text{Fe}}_{1-x}{\text{Co}}_x\right)}_2{\text{As}}_2$ superconducting compounds, $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$ shows strong evidence of competition and coexistence between superconductivity and antiferromagnetic order below the superconducting transition, $T_c=14\text{K}$. The transition temperatures for both the magnetic order and orthorhombic distortion are in excellent agreement with those inferred from resistivity measurements, and both order parameters manifest a distinct decrease in magnitude below $T_c$. These data suggest that the strong interaction between magnetism and superconductivity is a general feature of electron-doped $\text{Ba}{\left({\text{Fe}}_{1-x}T{M}_x\right)}_2{\text{As}}_2$ superconductors ($TM=\text{transition}$ metal).

Figure 1

(Color online) (a) X-ray and (b) neutron rocking curves of the $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$ sample investigated in this study. The picture shows the single crystal on a millimeter grid.

Figure 2

(Color online) (a) Measured magnetization of $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$ showing the superconducting transition at $T_c=14\text{K}$. (b) Resistance (points) and its derivative (line) showing the signature of $T_S$, $T_N$, and $T_c$. (c) Orthorhombic distortion measured as a function of temperature on cooling and warming. The inset shows an expanded region close to $T_c$ to emphasize the decrease in the orthorhombicity in the superconducting state. (d) Intensity of the nuclear (2 2 0) reflection as a function of temperature close to $T_S$ on cooling and warming, and the intensity of the (1/2 1/2 3) magnetic reflection on cooling and warming.

Figure 3

(Color online) Transverse scans through (a) the (1 1 10) charge reflection and (b) the (1/2 1/2 3) magnetic reflection demonstrating the transition between the tetragonal and orthorhombic structures and the onset of AFM order, respectively.

Figure 4

(Color online) (a) Measured orthorhombic distortions for $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$ and $\text{Ba}{\left({\text{Fe}}_{0.953}{\text{Co}}_{0.047}\right)}_2{\text{As}}_2$ as function of reduced temperature $T/T_S$. (b) Integrated intensity of the (1/2 1/2 3) magnetic reflections for $\text{Ba}{\left({\text{Fe}}_{0.961}{\text{Rh}}_{0.039}\right)}_2{\text{As}}_2$ and $\text{Ba}{\left({\text{Fe}}_{0.953}{\text{Co}}_{0.047}\right)}_2{\text{As}}_2$ normalized to their maximum value at $T_c$ plotted as function of reduced temperature $T/T_N$.