Neutron diffraction study of Sr2Mn2O5

The crystal and magnetic structure of SrMnO2.5 has been investigated by neutron power diffraction from 20 to 425 K. The compound has orthorhombic crystal structure with the unit cell dimensions a=0.55307(4), b=1.07829(8), c=0.38145(3) nm at 425 K, where space group is Pbam and Z=4. Below T-N=375 K, an antiferromagnetic order occurs and the magnetic unit cell is orthorhombic with the dimensions a(m) = a(c), b(m), = b(c), c(m) = 2c(c), where a(c), b(c) and c(c) are the parameters of the crystallographic unit cell. The ferromagnetic and antiferromagnetic coupling coexist in the c-plane according to the difference of Mn-O-Mn angle and the coupling between adjacent planes is antiferromagnetic. The direction of the magnetic moments is along the crystallographic b-axis. The magnitude of magnetic moment at 20 K is 3.44 mu(B)/Mn. (C) 2000 Published by Elsevier Science S.A. All rights reserved.