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College Park, Maryland      June 6 - 10 , 2004

WP59: Comprehensive analysis of spin dynamics in stripe-ordered La2-xSrxNiO4

H. Woo (Physics Department, Brookhaven National Laboratory; ISIS, Rutherford Appleton Laboratory), J. M. Tranquada (Physics Department, Brookhaven National Laboratory), A. T. Boothroyd (University of Oxford, U. K.), K. Nakajima (University of Tokyo, Japan), T. G. Perring, C. Frost (ISIS, Rutherford Appleton Laboratory), P. G. Freeman, D. Prabhakaran (University of Oxford, U. K.), K. Yamada (University of Tokyo, Japan)

The nature of the magnetic excitations in stripe-ordered nickelates and cuprates is a topic of considerable current interest. Here we will present measurements of spin waves in La2-xSrxNiO4 ( x = 0.275 and 1/3). The data, collected on the MAPS spectrometer at ISIS, provide a comprehensive mapping of the spin excitations throughout the two-dimensional Brillouin zone. We analyze the results using linear spin-wave theory[1], and show that the data provide a clear choice between two alternative models for effective exchange coupling through the charge stripes. The success of semi-classical spin-wave theory for describing excitations in stripe-ordered nickelates contrasts with its failure in the recently studied case of La1.875Ba0.125CuO4 [2].

HW and JMT are supported by the Office of Science, U.S. DOE under Contract No. DE-AC02-98CH10886.

[1] Boothroyd et al. Phys. Rev. B 67, 100407(R) (2003).

[2] Tranquada et al., cond-mat/0401621.

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