Magnetic structure of Cd-doped $\mathrm{Ce}\mathrm{Co}{\mathrm{In}}_5$

The heavy-fermion superconductor $\mathrm{Ce}\mathrm{Co}{\mathrm{In}}_5$ is believed to be close to a magnetic instability, but no static magnetic order has been found. Cadmium doping on the In site shifts the balance between superconductivity and antiferromagnetism to the latter with an extended concentration range where both types of order coexist at low temperatures. We investigated the magnetic structure of nominally 10% Cd-doped $\mathrm{Ce}\mathrm{Co}{\mathrm{In}}_5$, being antiferromagnetically ordered below $T_N\approx 3\mathrm{K}$ and superconducting below $T_c\approx 1.3\mathrm{K}$, by elastic neutron scattering. Magnetic intensity was observed only at the ordering wave vector $Q_{\mathrm{AF}}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ commensurate with the crystal lattice. Upon entering the superconducting state, the magnetic intensity seems to change only little. The commensurate magnetic ordering in $\mathrm{Ce}\mathrm{Co}{\left({\mathrm{In}}_{1-x}{\mathrm{Cd}}_x\right)}_5$ is in contrast to the incommensurate antiferromagnetic ordering observed in the closely related compound $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$. Our results give insights into the interplay between superconductivity and magnetism in the family of $\mathrm{Ce}T{\mathrm{In}}_5$ ($T=\mathrm{Co}$, Rh, and Ir) based compounds.

Figure 1

Doping-temperature $\left(x\text{−}T\right)$ phase diagram of $\mathrm{Ce}\mathrm{Co}{\left({\mathrm{In}}_{1-x}{\mathrm{Cd}}_x\right)}_5$, where $x$ is the nominal Cd concentration. Diamonds indicate the Néel temperature $T_N$ and circles the superconducting transition temperature $T_c$ determined by specific heat measurements. The arrow indicates the concentration investigated in this work, with transition temperatures as indicated by the solid symbols. Open symbols represent data taken from Ref. 8.

Figure 2

Temperature dependence the specific heat, $C_{\text{total}}-C_{\mathrm{La}\mathrm{Co}{\mathrm{In}}_5}$, for $\mathrm{Ce}\mathrm{Co}{\left({\mathrm{In}}_{0.9}{\mathrm{Cd}}_{0.1}\right)}_5$. The contribution of the nonmagnetic reference compound $\mathrm{La}\mathrm{Co}{\mathrm{In}}_5$ (Ref. 11) was subtracted from the specific heat of $\mathrm{Ce}\mathrm{Co}{\left({\mathrm{In}}_{0.9}{\mathrm{Cd}}_{0.1}\right)}_5$. The Néel temperature $T_N$ and the superconducting transition temperature $T_c$ are indicated by arrows. The inset shows the electrical resistivity measured on the same sample.

Figure 3

Elastic scans along [001] across $Q=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ in $\mathrm{Ce}\mathrm{Co}{\left({\mathrm{In}}_{0.9}{\mathrm{Cd}}_{0.1}\right)}_5$ at different temperatures. No magnetic intensity can be resolved at $T=3.22\mathrm{K}$ ($>T_N$, as determined by specific heat). The solid lines are Gaussian fits to the data.

Figure 4

Temperature dependence of the integrated magnetic intensity as obtained by Gaussian fits to the scans across $Q=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$.