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Mar 20 – 23, 2023
Campus Garching
Europe/Berlin timezone

Controlling the magnetic structure in W-type Hexaferrites

Mar 20, 2023, 2:00 PM
30m
MW 0 001 - Lecture hall (Fakultät für Maschinenwesen)

MW 0 001 - Lecture hall

Fakultät für Maschinenwesen

666
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Talk (25 + 5 min) Chemistry of Materials (Structure and Spectroscopy) Magnetic Structures

Speaker

Mathias Mørch (Aarhus University)

Description

Hexaferrites are important metal oxides, widely used as both permanent magnets and microwave absorbers. Recently, hexaferrites have attracted great interest, because they show magnetoelectric effects at room temperature. [1,2]
We have synthesized W-hexaferrites with varied Co/Zn ratio and investigated the magnetic order using neutron powder diffraction. In SrCo2Fe16O27 and SrCoZnFe16O27 a planar (Cm’cm’) magnetic ordering was found, rather than the uniaxial (P63/mm’c’) found in SrZn2Fe16O27, which is common in most W-type hexaferrites. Furthermore, in all three studied samples, non-collinear terms were present in the magnetic ordering, one of which is common to the planar ordering in SrCo2Fe16O27 and uniaxial ordering in SrZn2Fe16O27.
These non-collinear terms could be a sign of an imminent transition in the magnetic structure, which is further supported by thermomagnetic measurements. The thermomagnetic measurements revealed magnetic transitions at 520 and 360 K for SrCo2Fe16O27 and SrCoZnFe16O27, and Curie temperatures of 780 and 680 K, respectively, while SrZn2Fe16O27 showed no transition, but a Curie temperature at 590 K. Conclusively the magnetic transition can be adjusted by fine-tuning the Co/Zn stoichiometry in the sample. We believe a stoichiometry near SrCo0.65Zn1.35Fe16O27 would have the magnetic transition at room temperature, possibly giving rise to room temperature magnetoelectric effects.[3]

[1] Kitagawa, Yutaro, et al. "Low-field magnetoelectric effect at room temperature." Nature materials 9.10 (2010): 797-802.
[2] Song, Y. Q., et al. "Spin reorientation transition and near room-temperature multiferroic properties in a W-type hexaferrite SrZn1. 15Co0. 85Fe16O27." Journal of Applied Physics 115.9 (2014): 093905.
[3] Morch, M.I, Christensen M. “Controlling the Magnetic Structure in W-type Hexaferrites” Submitted

Primary author

Mathias Mørch (Aarhus University)

Co-author

Mogens Christensen (Aarhus University)

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