First-principles study of magnon-phonon interactions in gadolinium iron garnet

Abstract

We obtained the spin-wave spectrum based on a first-principles method of exchange constants, calculated the phonon spectrum by the first-principles phonon calculation method, and extracted the broadening of the magnon spectrum, ∆ω, induced by magnon-phonon interactions in gadolinium iron garnet (GdIG). Using the obtained exchange constants, we reproduce the experimental Curie temperature and the compensation temperature from spin models using Metropolis Monte Carlo (MC) simulations. In the lower-frequency regime, the fitted positions of the magnon-phonon dispersion crossing points are consistent with the inelastic neutron scattering experiment. We found that the ∆ω and magnon wave vector k have a similar relationship in YIG. The broadening of the acoustic spin-wave branch is proportional to k 2 , while that of the YIG-like acoustic branch and the optical branch are a constant. At a specific k, the magnon-phonon thermalization time of τmp are approximately 10 −9 s, 10 −13 s, and 10 −14 s for acoustic branch, YIG-like acoustic branch, and optical branch, respectively. This research provides specific and effective information for developing a clear understanding of the spin-wave mediated spin Seebeck effect and complements the lack of lattice dynamics calculations of GdIG. arXiv:1912.10432v1 [cond-mat.mtrl-sci] 22 Dec 2019 Gd Fe T O J dc J ac J aa J dd J ad J aa J dd J ad J ac J dc J

Magnon-magnon interaction and magnon relaxation time in a ferromagnetic Cr2Ge2Te6 monolayer

“…The Hall effect (including spin Hall effect, anomalous Hall effect and thermal Hall effect) in 2D magnets also attracts substantial attention, which not only promotes the development of novel Hall devices but also provides a new route to detect the existence of magnetism [40][41][42][43][44]. Among these Hall effects, the thermal Hall effect is related to the coupling between spin wave and lattice vibration (magnon-phonon coupling) [45], and the magnon-phonon coupling is usually studied by Raman spectra [46,47] phonon spectrum [48,49] and spin-wave spectrum [50,51]. In spintronics, the manipulation of magnetic order also is a hot topic, and there are numerous manipulation strategies, such as stack [52,53], electrostatic doping [54,55], and pressure [56,57].…”

Magnon hybridization in ferrimagnetic heterostructures

“…In this subsection, we present the hybrid magnon spectrum and wave functions in a YIG-GdIG [001] bilayer system with YIG and GdIG layers 6-unit-cellthick (7.4 nm) and 2-unit-cell-thick (2.5 nm), respectively. We adopt J aa ij = −0.329meV, J dd ij = −1.161meV, J ad ij = −3.449meV and S a,i = S d,i = 2.5 for the YIG layer [31] and J aa ij = −0.081meV, J dd ij = −0.137meV, J ad ij = −2.487meV, J ac ij = 0.032meV, J cd ij = −0.157meV, S a,i = 2.1, S d,i = 2.05 and S c,i = 3.5 for the GdIG and interfacial regions [35]. Fig.…”

“…The magnon dispersions in the two parts of this bilayer system are sketched in the upper panel of Fig. 1(b), where the two bands in the two layers are of opposite chiralities with the gap in YIG larger than that in GdIG [31,32,35].…”

“…Recently, Gomez-Perez et al showed that near the interface between YIG and GGG, the Gd atoms from GGG can diffuse into the YIG layer and substitute Y atoms in YIG, forming a natural YIG-GdIG magnetic bilayer [30], where the thickness of the GdIG layer is around 3 nanometers. Theoretically, whereas the magnon spectra in both YIG and GdIG have been studied in literatures [31][32][33][34][35], the hybrid magnon spectrum in their hybrid system is still missing. On the other hand, although GdIG shares the same structure with YIG, its SSE [36] is found to be quite different from that in YIG [9,37].…”

Effective Field Theory of Dark Matter Direct Detection With Collective Excitations

“…Second, we borrow the crystal potential of Y 3 Ga 5 O 12 (YGG) which is publicly available [95]. YGG has the same crystal structure as YIG, with Fe replaced by Ga, and the phonon dispersions we obtain for YGG are very similar to those of YIG [96]. The resulting reach is shown by the solid blue curve in Fig.…”