Single crystal neutron diffraction studies of low-temperature magnetic spin reorientation in Ca2Fe2O5
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Date
2013-12-15
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Australian Institute of Nuclear Science and Engineering
Abstract
Ca2Fe2O5 is a canted antiferromagnet (T{sub N} = 720 K) ) which displays an anomalous elevation in its magnetic susceptibility for 60 K T < 140 K. Based on susceptibility measurements performed on oriented single crystals, Zhou et al. [2] proposed a reorientation of the antiferromagnetic (AFM) easy-axis from the crystallographic a axis to the c axis below 40 K, proceeding via a region of minimal magnetocrystalline anisotropy in the anomalous temperature interval. In order to test this proposition, we have refined the atomic and magnetic structure of Ca{sub 2}F{sub e}2O{sub 5} against high-quality neutron Laue diffraction data collected on floating-zone-grown single crystals between 10 K and 300 K. An ad hoc sample mount was designed to apply a small (-35 Oe) magnetic field to the sample, ensuring perfect compatibility with the magnetic susceptibility data, which were also collected in a small field. Our refinements against both zero-field and in-field diffraction data reproduce the G-type AFM structure of Ca{sub 2}Fe{sub 2}O{sub 5} excellently at room temperature, including the known ferromagnetic canting. Careful examination of the refinement results reveals that the material is in fact best described by the room-temperature magnetic structure model as low as T=10 K, while the intermediate interval (measured at T=100 K) is characterised by subtle changes in the magnetic structure, including a reversal of the magnitudes of the magnetic moments on the two distinct Fe{sup 3+} sites.
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Keywords
Superfluidity, Neutron diffraction, Monocrystals, Superconductivity, Antiferromagnetic materials, Temperature dependence, Crystal structure, Laue method, Magnetic moments, Orientation
Citation
Auckett, J. E., Ling, C. D., McIntyre, G. (2013). Single crystal neutron diffraction studies of low-temperature magnetic spin reorientation in Ca2Fe2O5. Presented at AANSS 2013 11th Neutron Scattering Symposium, Sydney, NSW, 2-3 Dec. In 11th AINSE-ANBUG Neutron Scattering Symposium Abstracts, 2013, pp. 48.