Low-temperature magnetic structure of Ca2Fe2O5 determined by single-crystal neutron diffraction

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Australian Institute of Physics
Ca2Fe2O5 is a canted antiferromagnet (TN = 720 K) which displays an anomalous elevation in its magnetic susceptibility for 60 K < T < 140 K. [1] 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 Ca2Fe2O5 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 Ca2Fe2O5 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 at all measured temperatures, though in the intermediate temperature interval (measured at T = 100 K) the spins may be less well-ordered due to competing sublattice interactions.
Charged particles, Coherent scattering, Dielectric materials, Diffraction methods, Ions, Magnetic properties, Materials, Orientation, Physical properties
Auckett, J. E., Ling, C. D., McIntyre, G. J., & Avdeev, M. (2014). Low-temperature magnetic structure of Ca2Fe2O5 determined by single-crystal neutron diffraction. Paper presented at the 38th Annual Condensed Matter and Materials Meeting 2014, Waiheke Island Resort, Waiheke, Auckland, New Zealand, 4th February - 7th February, 2014. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2014/Wagga2014proceedings.pdf