Probing strong magnon-magnon coupling in a magnonic hybrid system*

Magnon based hybrid systems have attracted increasing interest due to their potential application in coherent information processing. We demonstrate electrical and optical detection of hybrized magnon-magnon dynamics in exchange-coupled nm-thick yttrium iron garnet/permalloy (YIG/Py) bilayer devices using spin rectification and Brillouin light scattering at room temperature.  The  uniform mode in  the  conductive  Py  layer  and  the first perpendicular standing spin-wave modes in the insulating YIG layer are coupled through interfacial exchange. We observe a magnon-magnon coupling strength of 9 mT for YIG(84 nm)/Py(10 nm). The introduction of a thin insulating SiO$_2$ layer between YIG and Py strongly suppresses the hybrid dynamics. Our work explores hybrid magnonic dynamics that are important in the implementation of coherent data processing.