Magnetism and superconductivity in CeCo(In,Cd) probed by SR

Oishi, Kazuki; Heffner, R. H.; Spehling, J.*; MacDougall, G. J.*; Ito, Takashi   ; Higemoto, Wataru  ; Amato, A.*; Nieuwenhuys, G.*; Klauss, H. H.*; Luke, G. M.*; Thompson, J. D.*; Bianchi, A.*; Fisk, Z.*

The heavy fermion superconductor CeCoIn has the highest critical temperature ( = 2.3 K) of the Ce-based 115 materials. Recently, it has been found that Cd substitution on the In site drives the system towards antiferromagnetism (AFM). Recent NMR studies suggest that the magnetism develops locally in the vicinity of the Cd atoms. Neutron scattering experiments on a sample with a nominal Cd concentration of 10% showed the coexistence of superconductivity and AFM. The AFM order develops below with the commensurate wave vector = (1/2, 1/2, 1/2) and the magnetic intensity did not increase below . We have performed SR measurements on single crystalline samples of Cd-doped CeCoIn at nominal Cd concentrations of 3%, 10% and 15% in order to further elucidate the magnetic and superconducting properties of CeCo(In,Cd). The crystallographic axis was aligned along the initial muon spin for both zero and in applied fields. In contrast to neutron scattering, SR can independently measure both the magnitude of the local field and the magnetic volume fraction. Muon spin precession signal was observed below in both the 10% and 15% Cd-doped samples, with different fractions of precession asymmetry. No magnetic signal in zero applied field was observed for the 3% sample.