Romain Lebrun(1), Andrew Ross(1,2), Asaf Kay(3), David Ellis(3), Daniel Grave(3), O. Gomonay(1,2,) Lorenzo Baldrati(1), Alireza Qaiumzedah(4), Camilo Ulloa(5), J. Sinova(1,2), Arne Brataas(4), Avner Rothschild(3), Rembert Duine(4,5,6) and Mathias Kläui(1,2,3,4)
1 Institute for Physics, Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
2 Graduate School of Excellence Material Science in Mainz, Staudingerweg 9, 55128, Mainz, Germany
3 Department of Materials Science and Engineering, Technion-Israel Institute of Technology
4 Center for Quantum Spintronics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
5 Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands
6 Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
In contrast to ferromagnets, antiferromagnets benefit from unparalleled stability with respect to applied external fields, magnetization dynamics at THz frequencies and a lack of stray fields [1]-[2]. Many theoretical studies have been undertaken describing the mechanisms through which antiferromagnets could allow for the propagation of spin current across the long distances which would be required for integration into information transfer and logic devices [3]-[4]. Recently, we demonstrated that in antiferromagnetic insulators, a diffusive magnonic spin current is able to propagate over tens of micrometers carried by the intrinsic Néel order using a single crystal of the most common insulating antiferromagnet, hematite (α-Fe2O3)[5]. With low damping and characteristic frequencies of hundreds of GHz, this compound allows for antiferromagnetic spin-waves to propagate as far as in YIG, a ferromagnetic material with the lowest known damping that is the material of choice for magnonic devices. Through measurements of the spin Hall magnetoresistance, the internal crystal anisotropies can be extracted [6], allowing for a precise determination of critical fields without the need for high frequency resonance experiments.
Here, we grow high quality antiferromagnetic thin films of hematite (< 500 nm) and show that they can also allow pure magnonic current to propagate over long-distances, opening the way towards a development and an integration of antiferromagnetic magnonic devices. We then discuss the role of the growth orientation and of the magnetic fields required to induce transport. By controlling the antiferromagnetic domains, we demonstrate how magnetic textures impact the propagation of polarized magnons [7]. Finally, we discuss the temperature dependence of the magnon propagation for magnons originating from an electrical spin-bias at the interface of hematite and platinum or from thermal heating of the hematite layer, and demonstrate that one can even achieve zero-field, room temperature magnon transport in insulating antiferromagnets.
[2] V. Baltz et al., Rev. Mod. Phys. 90, 015005 (2018)
[3] S. Takei et al., Phys. Rev. B, 90, 94408 (2014)
[4] S. Bender et al., Phys. Rev. Lett. 19, 056804 (2017)
[5] R. Lebrun et al., Nature 561, 222-225 (2018)
[6] R. Lebrun et al., Communications Physics 2 50 (2019)
[7] A. Ross et al., arXiv:1907.02751 (2019)