Speaker
Description
The rare earth iron garnets (IGs, REFe$_5$O$_{12}$, where RE is a rare earth) have been a source of scientific interest for decades due to their ferrimagnetic properties [1] and corresponding magnon dynamics [2]. The most famous rare earth IG, YIG, is the cornerstone of advances in spintronic technology, due to its exceptionally low magnon damping, microwave and magneto-optical properties [2]. Less well known are the magnetic excitations of other rare earth IGs, such as LuIG.
The rare earth IGs are described by space group $Ia3d$. The distribution of magnetic Fe ions among different sites leads to ferrimagnetism. Lu, being the smallest of the rare earths, is more likely to create antisite defects within the material. When combined with doping on the non-magnetic and magnetic sites, this leads to phenomena such as the inverse Faraday effect [3] and the spin Seebeck effect [4]. Lu$_3$Fe$_4$Co$_{0.5}$Si$_{0.5}$O$_{12}$ is a specific example of doped LuIG with increased anisotropy due to the Co$^{2+}$ substitution. Inherent in this large unit cell are frustrated exchange interactions. In a thin film sample this led to a magnetic phase transition at 200 K and an additional cluster spin glass phase below 190 K [5].
We have now studied Lu$_3$Fe$_4$Co$_{0.5}$Si$_{0.5}$O$_{12}$ in the bulk, using a single crystal sample for inelastic neutron scattering on the PELICAN and TAIPAN instruments at ANSTO, and neutron diffraction on D10 at the ILL. Our results show a clear anisotropy gap and a smaller gap between the acoustic magnon modes compared to YbIG [6] and YIG [7], as well as magnetocrystalline anisotropy that is strongly temperature dependent. The key differences in the magnetic structure, spin wave spectra and exchange parameters will be discussed.
References
[1] R. Pauthenet. “Magnetic Properties of the Rare Earth Garnets”. Journal of Applied Physics 30.4, S290-S292 (1959).
[2] A. A. Serga, A. V. Chumak, and B. Hillebrands. “YIG magnonics”. Journal of Physics D: Applied Physics 43.26, 264002 (2010).
[3] A. H. M. Reid et al. “Optical Excitation of a Forbidden Magnetic Resonance Mode in a Doped Lutetium-Iron-Garnet Film via the Inverse Faraday Effect”. Physical Review Letters 105.10, 107402 (2010).
[4] R. Ramos et al. “Room temperature and low-field resonant enhancement of spin Seebeck effect inpartially compensated magnets”. Nature Communications 10.1, 5162 (2019).
[5] H. Yamahara, M. Seki, and H. Tabata. “High temperature spin cluster glass behavior in Co- and Si-substituted garnet ferrite thin films”. Journal of Magnetism and Magnetic Materials 501, 166437 (2020).
[6] V. Peçanha-Antonio et al. “Model for coupled $4f-3d$ magnetic spectra: A neutron scattering study of the Yb-Fe hybridization in Yb$_3$Fe$_5$O$_{12}$”. Physical Review B 105.10, 104422 (2022).
[7] A. J. Princep et al. “The full magnon spectrum of yttrium iron garnet”. npj Quantum Materials 2.1, 1-5 (2017).
| Topics | Magnetism and Condensed Matter |
|---|
