Critical curve in an antiferromagnetic superconductor with nonmagnetic impurities

The critical factor curve of a transition of the second kind in an antiferromagnetic superconductor (AFS) with nonmagnetic impurities has been studied. The AFS is described by using the mean-field model given by Nass, Levin, and Grest and assuming a one-dimensional electron band. They find that the points on the critical curve satisfy the thermodynamic stability condition for 0 ≤ α/sub 1 tau//Δ0 ≤ 5.04 and 0.49 ≤ H/sub Q tau//Δ0 ≤ 1.64. Here α1 is the inverse lifetime of a conduction electron for nonmagnetic impurity scattering, H/sub Q/ is the antiferromagnetic molecular field, Δ0 is the zero-temperature order parameter of a superconductor in the absence of H/sub Q/ and impurities. Further, α/sub 1 tau/ and H/sub Q tau/ denote the values of these quantities for points on the critical curve. For α/sub 1 tau//Δ0 > 5.04 and H/sub Q tau//Δ0 > 1.64, the phase transition from the superconducting to the normal state is always of the second kind. Some thermal properties of the system near the critical curve have also been investigated and they find that these depends dramatically on the impurity concentration