Neutron Scattering Study on Yttrium Iron Garnet for Spintronics

Abstract

Spin current -- a flow of the spin degree of freedom in matter -- has vital importance in spintronics. Propagation of the spin current ranges over a whole momentum space; however, generated spin currents are mainly detected in the long-wavelength limit. To facilitate practical uses of spintronics and magnonics, microscopic understanding of the spin current is necessary. We here address yttrium iron garnet, which is a well-employed ferrimagnet for spintronics, and review {\it in re} the momentum- and energy-resolved characteristics of its magnetism. Using {\it unpolarized} neutrons, we refined its detailed crystal and magnetic structure, and examined magnetic excitations through four decades (10~$\mu$eV-100~meV) using chopper spectrometers in J-PARC, Japan. We also measured mode-resolved directions of the precessional motion of the magnetic moment, i.e., magnon polarization, which carries the spin current in insulators through {\it polarized} neutron scattering, using a triple-axis spectrometer in ILL, France. The magnon polarization is a hitherto untested fundamental property of magnets, affecting the thermodynamic properties of the spin current. Our momentum- and energy-resolved experimental findings provide an intuitive understanding of the spin current and demonstrate the importance of neutron scattering techniques for spintronics and magnonics.

15 pages, 17 figures

References in corpus (8)

• Direct electronic measurement of the spin Hall effect
• Theory of magnon-driven spin Seebeck effect
• Magnon Polarons in the Spin Seebeck Effect
• Thermal spin dynamics of yttrium iron garnet
• Direct observation of magnon-phonon coupling in yttrium iron garnet
• First-Principles Study of Exchange Interactions of Yttrium Iron Garnet
• Temperature-Dependent Interplay of Dzyaloshinskii-Moriya Interaction and Single-Ion Anisotropy in Multiferroic BiFeO${}_3$
• Parity Broken Chiral Spin Dynamics in Ba${}_3$NbFe${}_3$Si${}_2$O${}_{14}$