Dy-Doping of Zn/Al Substituted Nickel Ferrite for Non-Collinear Magnetic Order

Zn/Al substituted nickel ferrite (NiZAF) has been reported to be a very promising ferrimagnetic insulator with a Curie temperature well above room-temperature which exhibits a very low intrinsic magnetic damping [1]. Thin films of this magnetic spinel can be prepared using pulsed laser ablation [1] or reactive magnetron sputtering from single targets [2] as well as co-sputtering to vary the individual constituents independently [3]. Element selective characterization allows to determine the incorporation of the cationic species [1,2] and correlate them with the desired magnetic properties [3]. Besides an intrinsic low magnetic damping also non-collinear spin textures such as skyrmions are of potential interest for spintronic or magnonic applications [4]. For magnetic spinel such non-collinear magnetic textures have been reported to be generated either by structural effects in nanoparticles or ultrathin films, e.g. [5] or by doping with trivalent rare earth ions such as Dy [6]. In this work we will report on a systematic growth series of NiZAF films which were doped with Dy by means of co-sputtering. Due to its large ionic radius Dy distorts the crystal structure of the hosting spinel and the low coercive field as well as the low magnetic damping significantly increase. Nonetheless, the Curie temperature well-above room-temperature remains and the spinel structure is maintained on a local scale as evidenced by x-ray linear dichroism studies. Upon Dy doping a local minimum in the zero-field cooled M(T) curves develops which can be taken as a first indication for a non-collinear spin-arrangement which will be subject to further investigations and the latest results for the magnetic texture will be presented.<br/><br/>[1] S. Emori <i>et al.</i>, Adv. Mater. <b>29</b>, 1701130 (2017)<br/>[2] J. Lumetzberger, M. Buchner, S. Pile, V. Ney, W. Gaderbauer, N. Daffé, M. V. Moro, D. Primetzhofer, K. Lenz, and A. Ney, Phys. Rev. B <b>102</b>, 054402 (2020)<br/>[3] J. Lumetzberger, V. Ney, A. Zakharova, D. Primetzhofer, K. Lenz, and A. Ney, Phys. Rev. B <b>105</b>, 134412 (2022)<br/>[4] A. Fert, N. Reyren, and V. Cros, Nat. Rev. Mater. <b>2</b>, 17031 (2017)<br/>[5] M. Hoppe, S. Döring, M. Gorgoi, S. Cramm, and M. Müller, Phys. Rev. B <b>91</b>, 54418 (2015)<br/>[6] M. L. Kahn and Z. J. Zhang, Appl. Phys. Lett. <b>78</b>, 3651 (2001)