Fermi surface evolution through a heavy-fermion superconductor-to- antiferromagnet transition: De Haas-van Alphen effect in Cd-substituted CeCoIn₅

We report the results of de-Haas-van-Alphen (dHvA) measurements in CeCoIn₅ and LaCoIn₅. Cd doping is known to induce an antiferromagnetic order in the heavy-fermion superconductor CeCoIn₅, whose effect can be reversed with applied pressure. We find a slight but systematic change of the dHvA frequencies with Cd doping in both compounds, reflecting the chemical potential shift due to the addition of holes. The frequencies and effective masses are close to those found in the nominally pure compounds with similar changes apparent in the Ce and La compounds with Cd substitution. We observe no abrupt change to the electron Fermi surface volume in the high field paramagnetic state for x∼ x_c corresponding to the onset of antiferromagnetic ordering at H=0 in CeCo (In_1-x Cd _x)₅. Our results make it unlikely that a change of Fermi surface from large to small accompanies the change in the ground state meaning that the Fermi surface of CeCoIn₅ doped with Cd likely includes a significant contribution from Cef electrons even for x> x_c.