  In magnonics, an emerging branch of wave physics characterized by low-energy
consumption, it is highly desirable to realize circuit elements within the
scope of spin-wave computing. Here, based on numerical simulations, we
demonstrate the functionality of the spin-wave diode and the circulator to
steer and manipulate spin waves over a wide range of frequency in the GHz
regime. They take advantage of the unidirectional coupling induced by the
interfacial Dzyaloshinskii-Moriya interaction to transfer the spin wave between
thin ferromagnetic layers in only one direction of propagation. Using the
multilayered structure consisting of Py and Co in direct contact with Pt, we
obtain sub-micrometer-size devices of high efficiency. In the diode, the power
loss ratio between forward and reverse direction reaches 22 dB, while in the
four-port circulator, the efficiency exceeds 13 dB. Thus, our work contributes
to the emerging branch of energy-efficient magnonic logic devices, where,
thanks to short wavelength of spin waves, it is possible to realize nanoscale
devices.
