Large surface acoustic wave nonreciprocity in synthetic antiferromagnets

Abstract

We have studied the transmission of surface acoustic waves (SAWs) in ferromagnetic/non-magnetic/ferromagnetic tryilayers. The SAW scattering matrix is studied for devices with various non-magnetic spacer thickness, which defines the strength of the interlayer exchange coupling. We find the SAW transmission amplitude depends on its propagation direction when the two ferromagnetic layers are coupled antiferromagnetically. The degree of such SAW nonreciprocity increases with increasing exchange coupling strength and reaches 37 dB/mm for a device with the thinnest spacer layer. These results show the potential of interlayer exchange coupled synthetic antiferromagnets for viable acoustic nonreciprocal transmission devices, such as circulators and isolators.

Chiral Magnetoacoustics

“…The pronounced nonreciprocal transmission of magnetoacoustic waves opens an avenue to build new types of miniaturized and energy-efficient microwave components, such as acoustic isolators or circulators [23,36,71,72,87]. A good magnetoacoustic isolator shows at the same time a low insertion loss IL and a high transmission nonreciprocity ΔS.…”

Forward volume magnetoacoustic spin wave excitation with micron-scale spatial resolution

“…The magnetoacoustic response at different frequencies, which lay within the wide transmission band of the TIDT, can be assigned to the spatially separated CoFe+Ga, CoFe, and CoFe+Pt magnetic micro-stripes. SAW-SW interaction with micron-scale spatial resolution can be interesting for future applications in magnonics and the realization of new types of microwave devices such as magnetoacoustic sensors 5,6,60 or microwave acoustic isolators 14,[19][20][21] . For instance, giant nonreciprocal SAW transmission was observed in magnetic bilayers and proposed to build re-configurable acoustic isolators 14,[19][20][21] .…”

“…SAW-SW interaction with micron-scale spatial resolution can be interesting for future applications in magnonics and the realization of new types of microwave devices such as magnetoacoustic sensors 5,6,60 or microwave acoustic isolators 14,[19][20][21] . For instance, giant nonreciprocal SAW transmission was observed in magnetic bilayers and proposed to build re-configurable acoustic isolators 14,[19][20][21] . In combination with TIDTs, acoustic isolators, which show in adjacent frequency bands different nonreciprocal behavior could be realized.…”

“…High flexibility in the design of these devices is possible since the properties of the SWs can be varied in a wide range of parameters. For instance, the SW dispersion can be reprogrammed by external magnetic fields or electrical currents 15,16 and more complex design of the magnet geometry 17,18 or use of multilayers 14,[19][20][21] allow for multiple dispersion branches with potentially large nonreciprocal behavior. Vice versa, SAW-SW interaction can be also used as an alternative method to characterize magnetic thin films, SWs, and SAWs 12,20,22,23 .…”

Acoustically driven magnon-phonon coupling in a layered antiferromagnet

“…Such works have laid the foundations for the active field of SAW-spintronics, in which dynamically applied strain can modulate magnetic properties [6,18]. This technique is mature for ferromagnets, and has recently been proven effective for multiferroics [19] and synthetic antiferromagnets [14,20], but a demonstration of SAW-driven magnon-phonon coupling in a crystalline antiferromagnet remains elusive.…”