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Magnon Spin Transport in Antiferromagnetic Insulators

Vendredi 26 avril 2024 à 11:00, Salle de séminaire 445, bâtiment 1005, CEA-Grenoble

Publié le 26 avril 2024
Matthias Opel
Walther-Meissner-Institute, Bavarian Academy of Sciences and Humanities, Garching, Germany​
Magnons are the quantized excitations of the spin system in magnetically ordered materials and offer a unique platform for future information technology. Antiferromagnets host pairs of spin-up and spin-down magnons. We describe them in terms of a magnonic pseudospin [1]. Its close analogy to the electronic spin led to the prediction of novel fascinating spin transport phenomena. The antiferromagnetic oxide α-Fe2O3 (hematite) harbors a finite anisotropic spin-spin (“Dzyaloshinskii-Moriya”) interaction with a slight canting of the sublattice magnetizations in the magnetic easy (0001) plane at room temperature, giving rise to a residual net magnetization [1,2]. Bilayers of epitaxial α-Fe2O3 and heavy metal Pt electrodes with a large spin-orbit coupling represent a prototypical system to investigate the spin-Hall magnetoresistance [2], as well as antiferromagnetic magnon propagation [1,3-5]. We study the spin transport in two-terminal devices and demonstrate the electrical magnon injection, diffusive magnon transport, and magnon detection. We observe the coherent precession of the magnonic pseudospin caused by the easy-plane anisotropy and the Dzyaloshinskii-Moriya interaction. By further applying an external magnetic field, we control this precession and interpret our observation as the magnonic analogue of the electronic Hanle effect [1,3]. It is found to behave non-reciprocally, since the precession frequency depends on the propagation direction [4]. The effect amplitudes are sensitive to the antiferromagnetic anisotropy [5]. Our findings unlock the high potential of antiferromagnetic magnonics towards the realization of electronics-inspired phenomena.

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