  Results of a comprehensive study by means of Brillouin spectroscopy,
complemented by Ferromagnetic Resonance characterization, of spin waves (SW)
propagating in Py/Pt bi-layers, characterized by pronounced interface
Dzyaloshinskii-Moriya interactions (IDMI) are reported. Non-conventional wave
behavior of SW travelling in opposite directions, characterized by
non-reciprocity with respect to the inversion of the sign of the SW
wave-number, has been revealed. The value of the effective IDMI constant D has
been estimated.
