Evolution of spin excitations in electron-doped Pr0.88LaCe0.12CuO4−δ

We briefly review results of recent neutron scattering experiments designed to probe the evolution of antiferromagnetic (AF) order and spin dynamics in the electron-doped Pr0.88LaCe0.12CuO4−δ as the system is tuned from its as-grown nonsuperconducting AF state into an optimally doped superconductor (Tc = 24 K) without static AF order. For under doped materials, a quasi-two-dimensional spin-density-wave was found to coexist with three-dimensional AF order and superconductivity. In addition, the low energy spin excitations follow Bose statistics. In the case of optimally doped material, we have discovered a magnetic resonance intimately related to superconductivity analogous to the resonance in hole-doped materials. On the other hand, the low energy spin excitations have very weak temperature dependence and do not follow Bose statistics, in sharp contrast to the as-grown nonsuperconducting materials.