Патент Японии In the method, a pre-selected working area of a graphene film with a linear dimension of 2,000 nm, which working area is divided into sections having a dimension of 50-100 nm, is subjected to the effect of a pulsed alternating magnetic field with a frequency of 3 terahertz that corresponds to the transition from a ground energy level, corresponding to the non-excited state of spin density, to a fourth working energy level of the excited state of spin density in the graphene film, thus causing spin density pumping. A spatially localized external magnetic field is generated around the edges of the working area, which resonantly reflects spinons with a working frequency of 0.5-1 terahertz that corresponds to the transition from a third working energy level to a second working energy level of the excited state of spin density, said spinons causing the induced coherent radiation of working frequency spin waves as they pass through the working area.