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SUMMARY:Resonant Ultrasound Spectroscopy: characterisation of elastic and 
 anelastic behaviour of metals\, ceramics and functional oxides associated 
 with ferroic\, multiferroic and normal-superconductor phase transitions - 
 Prof Michael A. Carpenter\, Department of Earth Sciences\, Cambridge
DTSTART:20200214T140000Z
DTEND:20200214T150000Z
UID:TALK137509@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Resonant ultrasound spectroscopy (RUS) has proved to be a powe
 rful method for routine investigation of the elastic and anelastic propert
 ies of small polycrystalline or single crystal samples of metals\, mineral
 s and functional oxides. The ideal shape is a rectangular parallelepiped w
 ith edge dimensions in the range ~1-5 mm. This is placed lightly between t
 wo piezoelectric transducers\, one of which stimulates natural acoustic re
 sonances in the frequency range ~0.1 – 1.2 MHz and the second of which d
 etects them. Elastic moduli which determine each individual resonance mode
  scale with f2 and the acoustic loss is determined as the inverse mechanic
 al quality factor\, Q-1 = f/f\, where f is the resonance frequency and 
 f is its width at half maximum height. Because no glue is required to k
 eep the sample in place\, it is easy to design instruments in which RUS sp
 ectra can be collected over wide temperature intervals and with the possib
 ility of adding simultaneous electric and/or magnetic fields. The main ins
 trument in Cambridge uses a cryogen-free Oxford Instruments Teslatron to a
 ccess temperatures down to ~2 K with an external magnetic field of up to 1
 4 Teslas. The high temperature instruments allow routine data collection a
 t temperatures up to ~1200 C.\n\nApplications include the quantitative 
 determination of bulk and shear moduli of ceramics and metal alloys and th
 e use of characteristic Debye-like loss behaviour to detect\, for example\
 , hydrogen in steel. The main application in Cambridge has been to investi
 gate the role and dynamics of strain coupling arising at phase transitions
 \, which may be ferroelectric\, (anti)ferromagnetic\, ferroelastic\, multi
 ferroic\, relaxor\, Jahn-Teller\, superconducting\, etc. Examples of the m
 ethodology and overall approach will be given of the elastic and anelastic
  behaviour associated with phase transitions in a number of materials\, in
 cluding (Ca\,Sr)TiO3 perovskites\, the multiferroic perovskite GdMnO3\, th
 e helical magnet Cu2SeO3 and the unconventional superconductor\, Ba(Fe0.95
 7Co0.043)2As2.\n\nReview article: Journal of Physics: Condensed Matter 26\
 , 263201 (2015)\n
LOCATION:Oatley Seminar Room\, Department of Engineering
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