Abstract
A spin current - a flow of spin angular momentum - can be carried either by spin polarised free electrons or by magnons, the quanta of a moving collective oscillation of localised electron spins - a spin wave. Traditionally, it was assumed, that a spin wave in a magnetic film with spin-sink-free surfaces can transfer energy and angular momentum only along its propagation direction. In this work, using Brillouin light scattering spectroscopy in combination with a theory of dipole-exchange spin-wave spectra, we show that in obliquely magnetized free magnetic films the in-plane propagation of spin waves is accompanied by a transverse spin current along the film normal without any corresponding transverse transport of energy.
Highlights
Spin waves can be used as carriers of a spin current in spintronic [1,2] and magnonic [3,4,5] signal-processing devices, as they enable transport of energy and spin angular momentum over long distances along their propagation direction [6,7,8]
In this work, using Brillouin light-scattering spectroscopy in combination with a theory of dipole-exchange spin-wave spectra, we show that in obliquely magnetized free magnetic films, the in-plane propagation of spin waves is accompanied by a transverse spin current along the film normal without any corresponding transverse transport of energy
In contrast with the case of in-plane magnetization, in obliquely magnetized films the transverse profiles of in-plane-propagating dipole-exchange spin waves are only quasistanding, and they may allow for the transport of a spin angular momentum along the film normal even in the absence of any spin sink
Summary
Spin waves (or their quanta, magnons) can be used as carriers of a spin current in spintronic [1,2] and magnonic [3,4,5] signal-processing devices, as they enable transport of energy and spin angular momentum over long distances along their propagation direction [6,7,8]. If a spin sink, i.e., an overlayer with strong spin-orbit coupling (such as Pt or Ta), is attached to the film, the absorption of magnons by such a spin sink leads to the appearance of spin and energy flows along the film normal [26,27] It allows for the detection of propagating spin waves in a large range of wavelengths [27], and it plays an important role in the development of magnon spintronics toward utilization of short-wavelength dipolar-exchange and exchange spin waves in nanosized devices [1]. These unconventional spin currents may be crucially important for applications in modern spintronics [28], where they can substantially influence the effects of spin pumping and spin-transfer torque at a film interface
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