Neutron-depolarization and small-angle neutron-scattering (SANS) measurements were performed to obtain some magnetic information in various spatial scales on the reentrant-spin-glass state of Ni77Mn23. The wavelength-dependent neutron polarization in the magnetic fields offered some information about the temperature-dependent magnetic-domain-wall motion and the magnetization rotation in domains, i.e., (1) the domain-wall motion decreases with decreasing temperature, and (2) the magnetization in each domain shows a rigid rotation at low temperatures and a dissipative nature at higher temperatures when applying a magnetic field. The SANS intensity peak at a finite momentum transfer q that appeared in the magnetic fields indicates the formation of a modulated structure of transverse spin components in the domain. The spin structure was interpreted as vortexlike so as to obtain a consistent interpretation about the low-temperature behavior of the period of oscillatory neutron polarization as a function of wavelength. The field and temperature dependences of SANS intensity were well interpreted in terms of the vortex spin structure. Finally, we had a picture that the magnetization process in the reentrant state is characterized by the nature of the domain-wall motion and the magnetization rotation that strongly correlates with the spin-modulated structure.
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