Accession Number : AD0664333

Title :   MAGNETOELASTIC AND MAGNETOSTATIC WAVES IN TIME-VARYING MAGNETIC FIELDS,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE MICROWAVE AND QUANTUM MAGNETICS GROUP

Personal Author(s) : Rezende,Sergio M.

Report Date : DEC 1967

Pagination or Media Count : 129

Abstract : The propagation of microwave magnetoelastic and magnetostatic waves in a ferromagnet subjected to pulsed magnetic fields is investigated both theoretically and experimentally. In the first part of the theoretical analysis, which is restricted to spatially uniform bias fields, the coupling between the magnetic and elastic systems is neglected. Using a coupled mode approach, it is found that plane spin waves propagate in magnetic field transients with negligible reflections, constant momentum and wavenumber, but variable frequency and power flow. These results are further elucidated by the study of a simple step transient case. The analysis is also extended to magnetostatic modes propagating in axially magnetized cylinders. In the presence of magnetoelastic interaction, the theory indicates that besides changes in frequency and in power flow, the field gradient causes group velocity modulation and changes in the time duration of wave packets. In addition there is an exchange of momentum between the different branches of the dispersion relation; this exchange is calculated in terms of critical field gradients. These critical gradients are given for both shear and longitudinal waves propagating along certain crystallographic directions. Experiments with magnetoelastic pulses in axially magnetized YIG rods confirm the theoretical predictions. (Author)

Descriptors :   (*MECHANICAL WAVES, STABILITY), (*MAGNETIC MOMENTS, WAVE PROPAGATION), GARNET, YTTRIUM COMPOUNDS, IRON COMPOUNDS, RADIOFREQUENCY PULSES, EXCITATION, MAGNETIC FIELDS, PROPAGATION, ELASTIC PROPERTIES, TRANSIENTS, L BAND, PHONONS, THESES

Subject Categories : Electricity and Magnetism
      Electromagnetic Pulses

Distribution Statement : APPROVED FOR PUBLIC RELEASE