Dissertations from ProQuest

Title

Temperature dependence of 937 GHz sound transmission through Invar

1992

Article

Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Graeme Dewar, Committee Chair

Second Committee Member

George Alexandrakis, Committee Member

Abstract

The temperature and magnetic field dependence of the transmission of 9.365 GHz longitudinal sound through polycrystalline Invar has been experimentally studied in the 77-300 K range and compared with a theoretical model. In this model, the transmitted signal is excited via changes in volume magnetostriction associated with the passage of a longitudinal sound wave. We close Invar due to its high volume magnetostriction. The sound was generated by stresses arising at the surface of an 81 $\mu$m thick Invar sample via the interaction of electromagnetic radiation with the magnetization in the presence of a static magnetic field. The sample was part of the common H wall between two similar microwave cavities tuned to resonate at 9.365 GHz. In the sample-field configuration studied, the microwave and static magnetic fields were parallel to each other and to the sample surface. To study the temperature dependence of the transmitted signal, we measured the power ratio (transmitted power/incident power) expressed in decibels (dB). Theoretical expressions for the electromagnetic wave propagation constant and for the sound waves and electromagnetic waves amplitudes were obtained in terms of measurable parameters. In agreement with the theory, the transmitted signal was field-independent and no modulation was observed at FMR field ($\approx$600 Oe). The theoretical power ratio decreased $\approx$9 dB between calculations for a sample at 300 K and 77 K. The experimental signal was relatively constant in the same temperature range. No sound attenuation was considered in our calculations, but the strength of the transmitted signal together with the fact that the sample was $\approx$9 times ticker than the skin depth, indicates that it was small. From the analysis of the experimental data were have concluded that, within the limitations of our experiments, the generation and transmission of longitudinal sound waves through polycrystalline Invar, as well as their reconversion to electromagnetic waves, is essentially a temperature-independent process at 9.365 GHz.

Keywords

Physics, Condensed Matter; Physics, Acoustics