Phonon generation by magnetic films

Abstract

The generation of microwave acoustic waves by the resonance modes in a magnetic film is discussed. An initial orienta-[SI, using permalloy films a t 9 Gc/s, described the phonon generation under a variety of conditions. Using a viewpoint similar to that of Bommel and Dransfeld, he gave equations of motion for the elastic waves with magnetostrictive driving terms. This helped to explain the observed polarizations of the acoustic waves, but left unexplained some anomalies on SWR. One such anomaly was the observation that some higher-order spin waves, which had wavelengths less than the phonon wavelength, apparently interacted more strongly with the phonons than some lower-order spin waves, which had wavelengths more nearly comparable to the phonon wavelength. At this point Kooi [6] proposed a new explanation for the inequality of the observed spin wave and phonon wavelengths. He utilized the idea, originally due to Portis [7], which postulates the existence of a variation in dc magnetization or 1388 PROCEEDISGS OF THE IEEE OCTOBER anistropy field through the film thickness. This model implies that nonsinusoidal spin-wave modes exist on

Damping of Magnetization Dynamics by Phonon Pumping

“…When a magnet is connected to a nonmagnetic insulator instead of a metal, angular momentum cannot leave the magnet in the form of electronic or magnonic spin currents, but they can do so in the form of phonons. Half a century ago it was reported [11,12] and explained [13][14][15][16] that magnetization dynamics can generate phonons by magnetostriction. More recently, the inverse effect of magnetization dynamics excited by surface acoustic waves (SAWs) has been studied [17][18][19][20] and found to generate spin currents in proximity normal metals [21,22].…”

“…where elastic constants and mass density of non-magnet and magnet can differ. A uniform precession of the magnetization interacts with the lattice deformation at the surfaces of the magnetic film [13,14] and at defects in the bulk. The present theory then holds when the thickness of the magnetic film d √ A, where A is the cross section area.…”

“…The present theory then holds when the thickness of the magnetic film d √ A, where A is the cross section area. The Kittel mode induces lattice distortions that are uniform in the film plane u α (r) = u α (z) [14]. The elastic energy density is then affected by shear waves only:…”

“…When ρc t ρc t (soft substrate) or when acoustic impedances are matched (ρc t =ρc t ), damping at the resonancekd = (2n + 1)π with n ∈ N 0 [14] simplifies to…”

Induced domains and periodic domain structures in electrically and magnetically ordered materials

“…£ÐÂÚÂÎÇ ±¥³, Ô×ÑÓÏËÓÑÄÂÐÐÞÇ Ä ÔÇÅÐÇÕÑàÎÇÍÕÓËÍÂØ, ÍÂÍ ÓÂÐÇÇ Ë ÒÓÇAEÒÑÎÂÅÂÎÑÔß [1,2], ÔÕÂÎË ËÔÒÑÎßÊÑÄÂÕß AEÎâ ÒÓÇÑÃÓÂÊÑÄÂÐËâ ÍÑÅÇÓÇÐÕÐÑÅÑ ÑÒÕËÚÇÔÍÑÅÑ ËÊÎÖÚÇÐËâ ÄÑ ÄÕÑÓÖá ÅÂÓÏÑÐËÍÖ [26 ë 28],  ÊÂÕÇÏ Ë AEÎâ ÅÇÐÇÓÂÙËË Ë ÒÓÇÑÃÓÂÊÑÄÂÐËâ ÂÍÖÔÕËÚÇÔÍËØ ÍÑÎÇÃÂÐËÌ [29 ë 33]. ±ÓË-ÚÇÏ Ä ÑÃÑËØ ÔÎÖÚÂâØ à××ÇÍÕËÄÐÑÔÕß ÒÓÇÑÃÓÂÊÑÄÂÐËâ Ô ÒÑÏÑÜßá ±¥³ ÃÞΠÊÐÂÚËÕÇÎßÐÑ ÄÞÛÇ, ÚÇÏ ÒÓË ËÔ-ÒÑÎßÊÑÄÂÐËË ÕÇØ ÉÇ ÐÇÎËÐÇÌÐÞØ ÏÑÐÑAEÑÏÇÐÐÞØ ÍÓËÔÕÂÎ-ÎÑÄ ÃÇÊ ±¥³.…”