  We have investigated the (0001) surfaces of several hexagonal manganite
perovskites by low-energy electron diffraction (LEED) in order to determine if
the surface periodicity is different from that of the bulk materials. These
LEED studies were conducted using near-normal incidence geometry with a low
energy electron microscope (LEEM)/LEED apparatus from room temperature to 1200
degrees Celsius and with an electron energy in the range of 15-50 eV.
Diffraction patterns showed features of bulk-terminated periodicity as well as
a 2\times2 surface reconstruction. Possible origins for this surface
reconstruction structure are discussed and comparisons are made with surface
studies of other complex oxides.
