Accession Number : AD0636386

Title :   TRANSIENT AND STEADY STATE ABSORPTION OF MICROWAVE POWER UNDER PARALLEL PUMPING. I. THEORY.

Corporate Author : RAYTHEON CO WALTHAM MASS RESEARCH DIV

Personal Author(s) : Joseph, R. ; Schlomann,E.

Report Date : 15 JUN 1966

Pagination or Media Count : 86

Abstract : The transient growth of the spin wave population in a microwave magnetic field applied parallel to the dc field is investigated. It is assumed that the sample is in thermal equilibrium before the initiation of the microwave pulse, and the rf field amplitude remains constant during the pulse. According to the theory the absorption coefficient approaches a steady state value below threshold, and grows indefinitely (as long as the field amplitude remains constant) above threshold. The results of detailed calculations concerning the steady state and the transient absorption are described. Above threshold the time dependence of the absorption coefficient is characterized by a very fast initial rise to an intermediate plateau or hump, a subsequent more gradual rise, and an approximately exponential rise at later times. As the absorption coefficient increases the field amplitude in the cavity decreases (assuming that the incident power remains constant). This reaction of the sample upon the field amplitude is taken into account in an approximate fashion. Because of this reaction the absorption coefficient approaches a new steady state above threshold. (Author)

Descriptors :   (*MICROWAVES, ADSORPTION), (*PUMPING(ELECTRONICS), *NUCLEAR SPINS), FERROMAGNETIC MATERIALS, FIELD THEORY, TRANSIENTS, POWER

Subject Categories : Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE