Neutron scattering study of the high Tc superconductors

摘要: We carried out systematic neutron scattering experiments to investigate the magnetic properties and their relationship high-Tc superconductivity, when materials are tuned from antiferromagnetic (AF) parent compounds superconducting regime. observed resonance mode in electron doped cuprate Nd1.85Ce0.15CuO4, demonstrating that is a general phenomenon superconductors regardless of holeor electron-doping. In Pr0.88LaCe0.12CuO4, local susceptibility displays two distinct energy scales broadly consistent with bosonic modes revealed by scanning tunneling microscopy experiments. These results indicate presence very strong spin excitations couplings cuprates. Shortly after discovery superconductivity Fe pnictides, we discovered phase diagram CeFeAsO1−xFx remarkably similar Besides CeFeAsO, lattice structures also PrFeAsO SrFe2As2 systems. Neutron measurements show SrFe2As2, spectrum consists Bragg peak at elastic position, gap, sharp spin-wave higher energies. Based on dispersion relation, estimated effective exchange coupling using Heisenberg model. order study nature interactions compound studied high CaFe2As2. Although waves entire Brillouin zone can be described an three-dimensional anisotropic Hamiltonian, magnetism this system neither purely nor itinerant; rather it complicated mix two. When pnictide into regime doping, low fluctuation dominated mode. optimally