  Boolean logic is the foundation of modern digital information processing.
Recently, there has been a growing interest in phenomena based on pure spin
currents, which allow to move from charge to spin based logic gates. We study a
proof-of-principle logic device based on the ferrimagnetic insulator Yttrium
Iron Garnet (YIG), with Pt strips acting as injectors and detectors for
nonequilibrium magnons. We experimentally observe incoherent superposition of
magnons generated by different injectors. This allows to implement a fully
functional majority gate, enabling multiple logic operations (AND and OR) in
one and the same device. Clocking frequencies of the order of several GHz and
straightforward down-scaling make our device promising for applications.
