Coherent Spin Pumping Originated from Sub-Terahertz Néel Vector Dynamics in Easy Plane α-Fe2O3/Pt

Abstract

We present a thorough study of spin-to-charge current interconversion in bulk and thin films of (0001) α-Fe2O3 /Pt heterostructures by means of all-optical polarization-controlled microwave excitation at sub-Terahertz frequencies. Our results demonstrate that coherent spin pumping is generated through excitations of both the acoustic and optical modes of antiferromagnetic resonance, provided that the corresponding selection rules are met for the relative orientation between the microwave magnetic field h_ac and the magnetic moment m_0 of the Hematite. In particular, our results unanimously show that while a microwave field with h_ac perpendicular to m_0 pumps a net spin angular momentum from the acoustic mode, spin pumping from the optical mode is only enabled when h_ac parallel to m_0, as expected from the selection rules imposed by the Neel vector dynamics. Our results support the current understanding of spin mixing conductance in antiferromagnetic/non-magnetic interfaces, contrary to recent reports where the absence of spin pumping from the optical mode in Hematite was interpreted as a cancellation effect between the diagonal and off-diagonal components of the spin mixing conductance. We also provide an explanation for the previously reported observations and show how the optical spin pumping actually vanishes for thin films, which we speculate being either due to an increased level of inhomogeneities or to insufficient film thickness for the optical mode to fully realize.

arXiv comment14 pages, 4 figures

References in corpus (18)

• Efficient metallic spintronic emitters of ultrabroadband terahertz radiation
• Spin pumping and spin-transfer torques in antiferromagnets
• Subterahertz spin pumping from an insulating antiferromagnet
• THz-Frequency Spin-Hall Auto-Oscillator Based on a Canted Antiferromagnet
• Gilbert damping phenomenology for two-sublattice magnets
• Measurement of spin pumping voltage separated from extrinsic microwave effects
• Room temperature antiferromagnetic resonance and inverse spin-Hall voltage in canted antiferromagnets
• Spin pumping and shot noise in ferrimagnets: bridging ferro- and antiferromagnets
• Determination of intrinsic damping of perpendicularly magnetized ultrathin films from time resolved precessional magnetization measurements
• Spin Pumping of an Easy-Plane Antiferromagnet Enhanced by Dzyaloshinskii-Moriya Interaction
• Spin Pumping and Inverse Spin Hall Voltages from Dynamical Antiferromagnets
• Excitation and Detection of THz Coherent Spin Waves in Antiferromagnetic $\alpha -\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$
• Antiferromagnetic resonance in $\alpha$-Fe${}_2$O${}_3$ up to its Néel temperature
• Quantifying Spin-Orbit Torques in Antiferromagnet/Heavy Metal Heterostructures
• Cross-sublattice Spin Pumping and Magnon Level Attraction in van der Waals Antiferromagnets
• Absence of cross-sublattice spin pumping and spin-transfer torques in collinear antiferromagnets
• Impact of magnetic anisotropy on the magnon Hanle effect in $\alpha$-Fe${}_2$O${}_3$
• Anisotropic Field Suppression of Morin Transition Temperature in Epitaxially Grown Hematite Thin Films