Andreas Ney1,Julia Lumetzberger1,Verena Ney1,Anna Zakharova2,Nieli Daffe2,Daniel Primetzhofer3,Fabrice Wilhelm4,Andrei Rogalev4
Johannes Kepler Universitat Linz1,SLS2,Uppsala University3,ESRF4
Andreas Ney1,Julia Lumetzberger1,Verena Ney1,Anna Zakharova2,Nieli Daffe2,Daniel Primetzhofer3,Fabrice Wilhelm4,Andrei Rogalev4
Johannes Kepler Universitat Linz1,SLS2,Uppsala University3,ESRF4
Zinc ferrite in thin-film form possesses a range of possible applications such as gas sensors, photocatalytic applications or as an interesting semiconducting material in spintronics with tunable magnetic properties including unconventional magnetic order due to intrinsic or extrinsic frustration. Zinc ferrite (ZnFe<sub>2</sub>O<sub>4</sub>) belongs to the family of normal spinels of the form AB<sub>2</sub>O<sub>4</sub>. In bulk form zinc ferrite is known to be antiferromagnetic with a low Néel-temperature [1]. The magnetic properties significantly change as a thin film, especially for a finite degree of inversion and/or off-stoichiometry where ferro(i)magnetic order up to room temperature can be found, e.g. [2]. In contrast, other studies report the existence of a spin-glass or cluster-glass behavior under various conditions in bulk [3] or in thin films [4] exhibiting a wide range of spin freezing temperatures. Here we present a systematic study of epitaxial, stoichiometric zinc ferrite thin films prepared using reactive magnetron sputtering over a wide range of preparation conditions which exhibit signatures of magnetic glassiness up to room temperature [5]. Using element-selective characterization with soft x-ray magnetic circular dichroism we can provide evidence for a finite degree of inversion accompanied by the formation of Zn on octahedral lattice sites as well as a finite magnetic polarization of Zn. In addition, hard x-ray linear dichroism allows a correlation of magnetic glassiness with disorder in the Zn cationic sublattice, which can be induced by increasing the sputtering power, thus further elucidating the microscopic origin for magnetic glassiness at unusually high temperatures exceeding room temperature.<br/> <br/>[1] J. M. Hastings and L. M. Corliss, Rev. Mod. Phys. <b>25</b>, 114 (1953)<br/>[2] V. Zviagin, M. Grundmann, and R. Schmidt-Grund, Phys. Status Solidi B <b>257</b>, 1900630 (2020)<br/>[3] M. A. Hakim, M. Manjurul Haque, M. Huc, and P. Nordblad, Phys. B: Condens. Matter <b>406</b>, 48 (2011)<br/>[4] Y. Yamamoto, H. Tanaka, and T. Kawai, Jpn. J. Appl. Phys. <b>40</b>, L545 (2001)<br/>[5] J. Lumetzberger, V. Ney, A. Zakharova, N. Daffe, D. Primetzhofer, F. Wilhelm, A. Rogalev, and A. Ney, Phys. Rev. B <b>107</b>, 144416 (2023)