Temperature dependence of spin fluctuations in underdoped LaSrCuO

Sato, Kentaro*; Matsuura, Masato*; Fujita, Masaki*; Kajimoto, Ryoichi  ; Ji, S.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka   ; Inamura, Yasuhiro  ; Arai, Masatoshi; Enoki, Masanori*; Yamada, Kazuyoshi*

We studied the temperature dependence of spin excitation in the underdoped LaSrCuO in a wide energy range. At low temperature, a clear magnetic signal emerging from incommensurate (IC) (0.50.09, 0.5) positions was observed. The low-energy (10 meV) IC signal was confirmed at 200K, while the IC signal gradually merges upon warming and turns into a single commensurate peak centered at (0.5, 0.5) at 300 K. The overall spectral shape above 60 meV measured at 5 K and 350 K was almost the same, meaning the weak thermal effect on the high-energy dispersion relation. This weak change in the high-energy dispersion is consistent with the localized spin picture, whereas the robust IC structure against the temperature would be difficult to explain within a simple stripe model.