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Ferrimagnets have been at the spotlight of spintronics as their properties can be conveniently engineered and they display intriguing dynamic behavior in the vicinity of the magnetic and angular momentum compensation, useful for device applications.1,2 Among ferrimagnets, rare-earth iron garners have attracted a particular attention due to their insulating character, perpendicular magnetic anisotropy, and long magnon diffusion lengths, enabling efficient current-induced magnetization control,3 domain wall and skyrmion motion,3,4 and spin transport in nonlocal devices.5
In this work, we will first discuss the structural, magnetic, and spintronic properties of epitaxial terbium iron garnet (TbIG) films, a ferrimagnetic insulator with compensation temperature (TM) close to room temperature. The samples are deposited by RF magnetron sputtering with crystallinity and epitaxy on various (substituted) GGG substrates. The films display perpendicular magnetic anisotropy induced by compressive strain and tunable structural and magnetic properties with annealing conditions. Studying the temperature evolution of the anomalous Hall effect in Pt/TbIG heterostructures allows us to determine the TM of the ferrimagnetic ordering, that is found to be approximately ~200 K, some 50 K lower than in bulk. This is attributed to the Tb deficiency of the films corroborated by x-ray photoelectron spectroscopy measurements.6 In the second part of the talk, we will show, for the first time, that the insulating TbIG films display electronic spin-valve behavior when combined with a ferrimagnetic metal and a nonmagnetic spacer. We measure a current-in-plane giant magnetoresistance effect arising from the spin-dependent scattering of electrons at the interface between the TbIG and the spacer layer. Although the magnitude of the effect is smaller than in fully metallic stacks, it provides a means to read out the perpendicular magnetization vector of the insulator in a simple two-terminal geometry. This finding constitutes a major breakthrough, as it allows the integration of insulating magnets in spintronics devices with a technologically-viable electrical read out scheme.7
References
[1] S. K. Kim, et al., Nature Materials 21, 24–34 (2022)
[2] C.O. Avci, et al., Nature Materials 16, 309–314 (2017)
[3] C.O. Avci, et al. Nature Nanotechnology 14, 561–566 (2019)
[4] S. Vélez, et al., Nature Nanotechnology 17, 834–841 (2022)
[5] L. J. Cornellissen, et al., Nature Physics 11, 1022–1026 (2015)
[6] S. Damerio and C.O. Avci Journal of Applied Physics 133, 073902 (2023) [7] S. Damerio, S. Zhang and C.O. Avci, in preparation (2023)
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