Angular dependence of antiferromagnetic order induced by paramagnetism in a d-wave superconductor.

Antiferromagnetic (AFM) order and a spatial order peculiar to Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, previously indicated in the quasi-two-dimensional d-wave superconductors CeCoIn5 with strong paramagnetic pair breaking (PPB) in a magnetic field parallel to the basal plane, are considered in the field configurations tilted from the basal plane within an approach assuming that the wavelength of the FFLO modulation is relatively long. It is demonstrated that, with increasing the tilt angle, both the AFM and FFLO orders are gradually suppressed, and that disappearance of the AFM order in the zero-temperature limit occurs at a lower angle than that of the FFLO state. Consequently, a nonmagnetic FFLO-ordered high-field superconducting phase is realized in an intermediate range of the tilt angle even at low enough temperatures. As the perpendicular field configuration (H ‖ c) is approached by the field tilt, the nonvanishing AFM order in real space tends to occur only close to the FFLO nodal planes in contrast to the high-field behavior in the H ⊥ c case. Further, in the field versus temperature (H-T) phase diagram, the AFM order reduces, at a higher angle, to an AFM quantum critical point lying at a lower field than HC2(O) as a consequence of competition between the field dependencies of the nesting condition and of PPB. These features of the AFM order and the resulting H-T phase diagram strikingly coincide with those seen in a recent NMR measurement on CeCoIn5 in tilted field configurations. [ABSTRACT FROM AUTHOR]