Spin dynamics of quasi-2D ferromagnet La<sub>1.2sub>Sr<sub>1.8sub>Mn<sub>2sub>O<sub>7sub>
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- 作者：Chatterji ; Tapan ; Regnault ; L.P. ; Thalmeier ; P. ; van de Kamp ; R. ; Schmidt ; W. ; Hiess ; A. ; Vorderwisch ; P. ; et. al.
- 关键词：Colossal magnetoresistance ; La<sub>1.2sub>Sr<sub>1.8sub>Mn<sub>2sub>O<sub>7sub> ; Ferromagnet ; 75.30.Ds ; 75.25.+z ; 72.15.Gd
- 刊名：Journal of Alloys and Compounds
- 出版年：2001
- 出版时间：August 9, 2001
- 年：2001
- 卷：326
- 期：1-2
- 页码：15-26
- 全文大小：431 K
文摘
Neutron scattering investigations of the magnetic ordering and spin waves have been carried out on the bilayer manganite La<sub>1.2sub>Sr<sub>1.8sub>Mn<sub>2sub>O<sub>7sub> which shows colossal magnetoresistance (CMR) effect close to the ferromagnetic phase transition T<sub>Csub>
s/glyphs/BQ4.GIF>128 K. The dispersions of both the acoustic and the optic modes along [100] and [001] have been measured and by using a effective localised spin model the complete set of exchange parameters has been determined. The strong anisotropy in the exchange interactions suggests that La<sub>1.2sub>Sr<sub>1.8sub>Mn<sub>2sub>O<sub>7sub> can be considered as a quasi two-dimensional ferromagnet consisting of weakly coupled ferromagnetic bilayers. Although an effective localised spin model can explain the spin wave dispersion for small momentum and energy transfers close to the zone centre, it is no longer valid for larger momentum and energy transfers close to the zone boundary. The energy widths of the spin waves are found to be much larger than the instrument resolution showing the dual localised–itinerant character of the electronic system.