Oral Presentation Crystal36-AXAA Conference 2026

Modifying the magnetic properties of Sr4.5Fe2(Cr/S)0.5O9 layered ferrites with chemical pressure (143398)

Daniel McKay 1
  1. The University of Sydney, Sydney, NSW, Australia

Complex layered oxides have various unique magnetic properties that make them particularly attractive for research. Sr4.5Fe2(Cr/S)0.5O9 is a novel 0201-1201 type layered ferrite with a non-centrosymmetric ordering not seen in most other 0201-1201 compounds.1 Previous studies of a chromium-incorporating analogue, Sr4.5Cr2.5O9, have shown unique magnetic properties including spin canting and a low antiferromagnetic coupling energy allowing for a metamagnetic transition.2 This study has characterised the structural and magnetic properties of Sr4.5Fe2(Cr/S)0.5O9 and further modified the structure by application of chemical pressure via Ca2+ doping. Samples of Sr4.5Fe2(Cr/S)0.5O9 were successfully synthesised via solid-state methods and structurally characterised by X-ray and neutron powder diffraction. Diffraction data indicated significant structural disorder localised to one of the structural layers; an effect which has been previously reported in 0201-1201 materials.3 Magnetic susceptibility measurements show antiferromagnetic order at low temperature for both Sr4.5Fe2Cr0.5O9 (T = ~45 K) and Sr4.5Fe2S0.5O9 (T = ~35 K), each with significant divergence of field-cooled and zero-field-cooled susceptibility curves below the ordering temperature. There is also a small ferromagnetic moment in both materials, indicated by a magnetic hysteresis at 2 K. Two plausible explanations for the development of this magnetic moment are spin-canting of Fe4+ and the formation of ferromagnetic and antiferromagnetic domains. Low-temperature neutron diffraction showed no long-range magnetic ordering in these materials in zero applied field, which may be related to the structural disordering. Application of chemical pressure by Ca2+ doping into Sr2+ sites was successful, indicated by a decrease in unit cell size and an increase in the structural disorder. Susceptibility measurements showed the appearance of new higher temperature magnetic transitions not seen in the undoped materials, that may be related to the increased strength of interlayer magnetic interactions.

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Figure 1; The crystal structure of Sr4.5Fe2Cr0.5O9 with the unit cell shown as the black dotted line.

  1. Jarvis, A.; Berry, F. J.; Marco, J. F.; Cibin, G.; Slater, P. R. Synthesis and Characterisation of the New Oxyanion Doped “0201–1201” Type Layered Oxide, Sr4.5Fe2(S/Cr)0.5O9±δ. Journal of Solid State Chemistry 2024, 338, 124822. https://doi.org/10.1016/j.jssc.2024.124822.
  2. Pelloquin, D.; Wahl, A.; Masset, A. C.; Maignan, A.; Michel, C.; Raveau, B. A Novel Mixed Valent Chromium-Layered Oxide with Peculiar Magnetic Properties: Sr4.5Cr2.5O9. Journal of Solid State Chemistry 2002, 154 (2), 375–383. https://doi.org/10.1006/jssc.2000.8798.
  3. Caignaert, V.; Daniel, Ph.; Nguyen, N.; Ducouret, A.; Groult, D.; Raveau, B. Structure Refinement of the 0201-1201 Intergrowth-Type Ferrite PbSr4Fe2O9: Powder Neutron Diffraction and Mösbauer Spectroscopy Studies. Journal of Solid State Chemistry 2002, 112 (1), 126–131. https://doi.org/10.1006/jssc.1994.1276.