We have measured the spin-wave spectrum of the half-doped bilayer manganite Pr(Ca,Sr)2Mn2O7 in its spin, charge, and orbital ordered phase. The measurements, which extend throughout the Brillouin zone and cover the entire one-magnon spectrum, are compared critically with spin-wave calculations for different models of the electronic ground state. The data are described very well by the Goodenough model, which has weakly interacting ferromagnetic zig-zag chains in the CE-type arrangement. A model that allows ferromagnetic dimers to form within the zigzags is inconsistent with the data. The analysis conclusively rules out the strongly bound dimer (Zener polaron) model.
@article{arxiv.1210.7108,
title = {Ground state in a half-doped manganite distinguished by neutron spectroscopy},
author = {G. E. Johnstone and T. G. Perring and O. Sikora and D. Prabhakaran and A. T. Boothroyd},
journal= {arXiv preprint arXiv:1210.7108},
year = {2013}
}
Comments
Published in Physical Review Letters. Supplementary material is available from the corresponding authors