Kimura H, Kofu M, Matsumoto Y, Hirota K
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
Phys Rev Lett. 2003 Aug 8;91(6):067002. doi: 10.1103/PhysRevLett.91.067002. Epub 2003 Aug 5.
Low-energy spin excitations of La(1.85)Sr(0.15)Cu(1-y)Zn(y)O4 were studied by neutron scattering. In y=0.004, the incommensurate magnetic peaks show a well-defined "spin gap" below T(c). The magnetic signals at omega=3 meV decrease below T(c)=27 K for y=0.008, also suggesting the gap opening. At lower temperatures, however, the signal increases again, implying a novel in-gap spin state. In y=0.017, the spin gap vanishes and elastic magnetic peaks appear. These results clarify that doped Zn impurities induce the novel in-gap state, which becomes larger and more static with increasing Zn.
