Unconventional Superconductivity in CeCoIn₅Studied by the Specific Heat and Magnetization Measurements

Effect of Disorder Induced by Heavy-Ion Irradiation on CeCoIn5 Superconductivity

“…2. Clearly M vs H of irradiated CeCoIn 5 shows more saturation as the field is increased 3 , where the reported [15] increase with saturation upon irradiation is significantly smaller than observed here for CeCoIn 5 . One of the interesting points to note for the irradiated CeCoIn 5 , the magnetization is negative for fields below H = 3000 gauss at T = 2 K while the magnetization remains negative for fields only below H = 1000 gauss at the same 2 K temperature for the unirradiated CeCoIn 5 .…”

“…Clearly M vs H of irradiated CeCoIn 5 shows more saturation as the field is increased 3 , where the reported [15] increase with saturation upon irradiation is significantly smaller than observed here for CeCoIn 5 . One of the interesting points to note for the irradiated CeCoIn 5 , the magnetization is negative for fields below H = 3000 gauss at T = 2 K while the magnetization remains negative for fields only below H = 1000 gauss at the same 2 K temperature for the unirradiated CeCoIn 5 . In summary, the increase in low-temperature susceptibilities and increased saturation in M vs H in irradiated CeCoIn 5 implies that the defects induced by the heavy ion irradiation are at least partly magnetic in their nature, just as found for UBe 13 and UPt 3 irradiated by neutrons.…”

“…The unusual properties of CeCoIn 5 have been investigated by various experiments such as specific heat [2,[4][5][6], magnetic susceptibility [5,7], resistivity [3,8], thermal conductivity [4], NMR T 1 measurement [9,10], and de Haas-van Alphen (dHvA) [8,11]. These results suggest an unconventional superconductivity in this complex compound.…”

“…An H-T phase diagram of CeCoIn 5 [2,5,7] shows that the upper critical field where its superconductivity disappears is H c2 = 5.1 T when the field parallel to the c-axis. At the same field, non-Fermi liquid (NFL) behavior has been reported from the results of a logarithmic temperature dependence of C/T up to about 10 K [6].…”

Superconductivity and Non-Fermi-Liquid Behavior in the Heavy-Fermion Compound CeCo1−xNixIn5

“…6) The magnetic origin of the SC pairing is inferred from the d-wave (d x 2 −y 2 ) symmetry of the SC gap determined by thermal conductivity, specific heat, and conductance measurements. [7][8][9] In magnetic fields, the spin degrees of freedom are significantly coupled with the stability of the SC order; a strong Pauli paramagnetic effect gives rise to a first-order transition at the SC upper critical field H c2 below 0.7 K, 7,[10][11][12] and the SC phase coexistent with AFM spin modulation evolves just below H c2 at very low temperatures. [13][14][15][16][17][18] Furthermore, the existence of the AFM-QCP at ∼ H c2 is strongly suggested from the observations of the NFL behavior in the paramagnetic phase above H c2 , including the − ln T divergence in specific heat divided by temperature, the T -linear dependence in magnetization, and electrical resistivity.…”