Field dependence of magnon decay in yttrium iron garnet thin films

Abstract

We discuss threshold field-dependence of the decay rate of the uniform magnon mode in yttriumiron garnet (YIG) thin films. We demonstrate that decays must cease to exist in YIG films of thickness less than 1 µm, the lengthscale defined by the exchange length. We show that due to symmetry of the three-magnon coupling decay rate is linear in ∆H = (Hc − H) in the vicinity of the threshold field Hc instead of the step-like Γ k=0 ∝ Θ (∆H) expected from the two-dimensional character of magnon excitations in such films. For thicker films, decay rate should exhibit multiple steps due to thresholds for decays into a sequence of the 2D magnon bands. For yet thicker films, such thresholds merge and crossover to the 3D single-mode behavior: Γ k=0 ∝ |∆H| 3/2 .

Nonlinear spin-current enhancement enabled by spin-damping tuning

“…Here for simplicity, we assume that the damping due to the three-magnon splitting as Z 3s ¼ G 3s (n q þ n À q ), where G 3s is the splitting strength. 5,30 Notably, the splitting strength G 3s increases with the decreasing excitation frequency f 0 , because the number of the degenerate states at f 0 /2 available for the splitting increases by decreasing f 0 (see also the schematic illustrations in Fig. 5c) 30 .…”

“…5,30 Notably, the splitting strength G 3s increases with the decreasing excitation frequency f 0 , because the number of the degenerate states at f 0 /2 available for the splitting increases by decreasing f 0 (see also the schematic illustrations in Fig. 5c) 30 . Thus, by decreasing f 0 below the cut-off frequency, the relative number of the small-damping dipole-exchange secondary magnons increases and that of the large-damping uniform magnons decreases (see also equation (2)), resulting in the long lifetime t of the spin system as demonstrated in Fig.…”

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

“…Therefore, the uniform mode can then in principle decay by splitting into magnons at the band minima assuming the kinematic requirements are met. Such magnon splitting through dipolar effects have been extensively studied in the similar compound YIG 70,[72][73][74] . Theoretical treatments which include dipolar effects are needed to determine if such effects can account for the observed decay of the uniform mode in Cu 2 OSeO 3 .…”

Role of dimensionality in spontaneous magnon decay: Easy-plane ferromagnet

“…The dependence of E(k 0 , q) on q enters only via a linear combination a q (14). Thus, neglecting higher-order terms one finds an effective 1D dispersion of the decay surface E(k 0 , q) = ω.…”

“…4,9,10 Besides that three-particle processes may produce a spectacular quantum effect: spontaneous magnon decay, which leads to a finite magnon lifetime even at T = 0. 11 Theoretical predictions of spontaneous magnon decay were made for dipolar ferromagnets, [12][13][14] for easy-plane ferromagnets, 15,16 and various noncollinear antiferromagnets, see literature cited in Ref. [11].…”