Frequency-crossing phonon spectrometer techniques.
An ac technique for measuring magnetothermal conductivities using frequency crossing has been developed and shows a 13-fold increase in signal-to-noise ratio over the conventional dc technique. The ac technique employs low-frequency field modulation coupled with phase-sensitive detection and a 45-fold improvement in signal-to-noise ratio may be obtained by modulation over the half-width of the frequency crossing signal. A further increase of approximately 3 would be obtainable by increasing the modulation frequency and overcoming technical problems. The limit of detection and instrument revolution may be as low as 10 in. spins and a few megahertz, respectively.
Wybourne
M N
MN
Department of Physics, University of Nottingham, University Park, Nottingham NG7 2RD, England.
Jefferies
D J
DJ
Challis
L J
LJ
Ghazi
A A
AA