The ultrasonic modulation technique of determining strain effects in ESR

Abstract

By replacing the magnetic modulation in an ESR experiment with strain modulation it is possible to determine strain effects in ESR simply and directly. The apparatus producing the strain modulation consists of two piezoelectric quartz crystals and a specimen vibrating in a longitudinal mode at 40 kHz. The stress applied to the specimen is longitudinal ( sigma /sub /// only) while the strain amplitude can range from a thermal limit of 10^-13 to a fracture limit of 10^-3. Because ultrasonically modulated electron spin resonance (UMER) enables a spectrum change due to strain to be measured directly rather than as a small difference between two large magnetic fields, it has been found to be more sensitive than other methods. The equipment for conducting UMER experiments is described and the theoretical basis for the method is discussed.