Hourglass dispersion in overdoped single-layered manganites
  The excitation spectrum in single-layered Nd(0.33)Sr(1.67)MnO4 and Pr(0.33)Ca(1.67)MnO4 resembles the hourglass-like excitation dispersion seen in various cuprates superconductors. However, our spin-wave dispersion in Pr(0.33)Ca(1.67)MnO4, which exhibits a large correlation length of the magnetic order, showing outward-dispersing branches starting from the incommensurate zone-centres. The magnetic correlation length is identified as the decisive parameter to suppress this branches and generating an correct hourglass shape. 
H. Ulbrich, P. Steffens, D. Lamago, Y. Sidis, M. Braden
cond-mat.str-el cond-mat.supr-con