Anisotropy of antiferromagnetic spin fluctuations in the heavy fermion superconductors of CeMIn5 and PuMGa5 (M=Co, Rh)

Abstract

AbstractThe anisotropy of antiferromagnetic spin fluctuations has been investigated microscopically in the heavy fermion systems of CeMIn5 and PuMGa5 (M=Co, Rh) by means of nuclear magnetic resonance (NMR). Both systems are known to be relatively high-Tc superconductors among the heavy fermion systems, especially PuCoGa5, which has a Tc=18.5 K almost one order of magnitude larger than for CeCoIn5 ( Tc=2.3 K). Analysis of the Knight shift and spin-lattice relaxation rates suggests XY-type anisotropy in the antiferromagnetic spin fluctuations in the normal states of these unconventional superconductors. Moreover, the 115 superconductors with larger XY-type fluctuations have a higher Tc, compared to the anisotropy of spin fluctuations in the related paramagnetic system UFeGa5 and antiferromagnets UPtGa5, NpCoGa5, NpFeGa5.