Interaction of magnetostatic waves with a current

It is shown that the interaction of magnetostatic waves with a current can be characterized by a coupling constant analogous to, but much greater than, the piezoelectric coupling constant. The theory is applied both to surface and forward‐traveling volume magnetostatic waves, and the problems of excitation, reflection, and absorption by a single microstrip and by a narrow‐band interdigital transducer are treated. It is found that the coupling constant is close to 0.5 for any reciprocal wave, and is greater for any nonreciprocal wave, when the transducer is in contact with the magnetic medium. These values are too large to allow effective signal processing, since the emitted waves react strongly on the transducer; narrow‐band transducers must be lifted above the surface so as to weaken the coupling.