Crystal and magnetic structures of the brownmillerite compound Ca2Fe1.039(8)Mn0.962(8)O5 |
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Authors: | Farshid Ramezanipour Bradley Cowie Shahab Derakhshan John E Greedan Lachlan MD Cranswick |
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Institution: | a Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1 b Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada L8S 4M1 c Canadian Neutron Beam Centre, National Research Council, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1J0 |
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Abstract: | The crystal and magnetic structures of the brownmillerite material, Ca2Fe1.039(8)Mn0.962(8)O5 were investigated using powder X-ray and neutron diffraction methods, the latter from 3.8 to 700 K. The compound crystallizes in Pnma space group with unit cell parameters of a=5.3055(5) Å, b=15.322(2) Å, c=5.4587(6) Å at 300 K. The neutron diffraction study revealed the occupancies of Fe3+ and Mn3+ ions in both octahedral and tetrahedral sites and showed some intersite mixing and a small, ∼4%, Fe excess. While bulk magnetization data were inconclusive, variable temperature neutron diffraction measurements showed the magnetic transition temperature to be 407(2) K below which a long range antiferromagnetic ordering of spins occurs with ordering wave vector k=(000). The spins of each ion are coupled antiferromagnetically with the nearest neighbors within the same layer and coupled antiparallel to the closest ions from the neighboring layer. This combination of intra- and inter-layer antiparallel arrangement of spins forms a G-type magnetic structure. The ordered moments on the octahedral and tetrahedral sites at 3.8 K are 3.64(16) and 4.23(16) μB, respectively. |
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Keywords: | Ca2FeMnO5 Brownmillerite Long range magnetic order Crystal and magnetic structure Neutron diffraction |
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