RADIOISOTOPES

High-transition-temperature superconductivity in cuprate oxide emerges by carrier-doping into Mott insulator, which has the spins with the quantum spin number of 1/2 and the strong superexchange interaction with the coupling constant of ～1500 K. Therefore, the study of spin dynamics in the cuprate superconductor by the neutron scattering technique is one of the most difficult and challenging research issues. However, an operation of new intense neutron sources and a recent development of instrumental techniques enable us to study the excitation spectrum in a wide energy-momentum space. As the results, we revealed the existence of hierarchical structure in the magnetic excitation of superconducting compounds. In this paper, we overview the features of the hierarchical magnetic excitation in cuprate superconductor and discuss the possible origin of the hierarchy on the basis of the results of the precise measurements carried out at the J-PARC/MLF.