  The antiferromagnetic order and structural distortion in the LaFe(As1-xSbx)O
system have been investigated by powder neutron diffraction and physical
properties measurements. Polycrystalline samples of LaFe(As1-xSbx)O (x<0.5)
were prepared using solid state synthesis at ambient and high pressure. We find
that the isoelectronic substitution of Sb for As decreases the structural and
magnetic transition temperatures but, contrary to the effects of phosphorus
substitution, superconductivity is not induced. Instead a slight increase in
the Fe magnetic moment is observed.
