Partial frustration of magnetic order in synthetic angelellite, Fe_4As_2O_(11)

摘要

The antiferromagnetic structure of Fe_4As_2O_(11) has been solved from neutron powder diffraction data below the Neel temperature of 159 K. A 2a X b X c magnetic supercell is adopted and the two crystallographically distinct Fe~(3+) sites order with different critical exponents and with saturated magnetic moments of 3.34(2) and 4.37(2) #mu#_B. The large difference between these magnetic moments reflects differing degrees of frustration at the two sites. Structural refinement using high resolution powder neutron diffraction data confirms the structural model previously reported and no evidence for the presence of an OH group associated with a very short Fe-O distance of 1.76(2) A is found.