1210.7108 (G. E. Johnstone et al.)

The ground state in a half-doped manganite distinguished by neutron
spectroscopy    [PDF]

G. E. Johnstone, T. G. Perring, O. Sikora, D. Prabhakaran, A. T. Boothroyd

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 zig-zags is inconsistent with the data. The analysis conclusively rules out the strongly bound dimer (Zener polaron) model.

View original: http://arxiv.org/abs/1210.7108