Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime.
Rectification of microwave oscillations of magnetization in a permalloy film is realized using planar Hall effect. Two different rectified signals are obtained: a signal from the linearly excited uniform magnetization precession at the frequency of the external pumping and a signal from the pairs of contra-propagating short-wavelength spin waves parametrically generated at a half of the pumping frequency. The second, most unusual, rectified signal is caused by the uniform component of the dynamic magnetization created due to the interference of the phase correlated pairs of parametric spin waves.The experimental investigations of phenomena caused by the spin-orbital interaction in magnetically ordered substances is one of the dominating directions in modern magnetism [1]. The spin-orbital effects like anisotropic magnetoresistance (AMR) [2], spin Hall [3] and inverse spin Hall [4] effects allow an experimentalist not only to detect the spin currents caused by linear and nonlinear the microwave magnetization dynamics (see e.g. Ref.[5]), but also to create pure spin currents that are sufficiently large to excite microwave auto-oscillations in magnetic metals [6]. Among the effects that allow one to electrically detect magnetization dynamics in magnetics the rectification effects, that are caused by the nonlinear coupling between the spin and charge dynamics and provide resultant signal in the form of a DC voltage, play a particularly important role, since they are sensitive not only to the geometric configuration of the detected microwave fields, but also to the phase and angular relations between the microwave fields and currents [7]. These effects can be used for the detailed probing of the magnetization dynamics in magnetic micro-and nano-structures [8] and, also, for the development of ultra-sensitive microwave detectors [9][10][11], demodulation of amplitude-modulated microwave signals [12], and for non-destructive testing [13].Here we present experimental evidence that another effect caused by the spin-orbital interaction, namely, the planar Hall effect (PHE) [14,15], can be successfully used for the detection and rectification of microwave signals exciting the oscillating magnetization dynamics in magnetic metals. In this case, the dependence of the detected DC voltage on the angle between the microwave magnetic field h(t), causing the effect, and the bias magnetic field H, magnetizing the magnetic metal, is qualitatively different from the angular dependence of the rectification voltage caused by the anisotropic magnetoresitance [2,14,16,17]. Moreover, the discovered PHE based rectification process produces DC voltage even in the case when the detected magnetization dynamics is associated with short-wavelength spatially non-uniform spin waves parametrically excited in the magnetic metal.Similarly to the conventional Hall effect, in case of the PHE the flow of the conduction electrons is deflected from the straight propagation path, but this deflection is not caused by the Lorentz force. It occurs due to t...
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