Magnetic field direction influence on the spectrum of spin waves output signals at three-magnon decay of magnetostatic surface waves in a cross based on waveguides of yttrium iron garnet film

Subject. We studied the effect of magnetic field $\vec{H}$ direction on the spectrum of the output signals in a 4-port cross-shaped structure where magnetostatic surface waves (MSSW) are excited by an input transducer under the condition of the first-order parametric instability (three-magnon). Objective. To detect the influence of nonreciprocal effects on the development of parametric instability of spin waves (SW) in tangentially magnetized multiport microstructures based on films of yttrium iron garnet (YIG). Methods. The experiments were carried out for a cross structure from YIG film with the thickness $d\approx 3.8 $ $\mu$m, in the form of two orthogonal waveguides having a width $w\approx500$ $\mu$m and a length $L\approx 3$ mm with the SW wire antennas placed at the ends of the waveguides, where one of antennas on the transversely magnetized waveguide was considered as an input. Results. It has been found that at the output antennas located near the ends of the longitudinally magnetized waveguide and oriented perpendicular to magnetic field, the SW spectra are qualitatively different and nonreciprocal with respect to the field direction $\vec{H}$ or to the change in the propagation direction of the MSSW pumping signal. Discussion. The observed effect is associated with the nonreciprocal character of propagation of both the pumping wave and waves generated at parametric instability condition.