Kavli Affiliate: Brad J. Ramshaw
| First 5 Authors: Mark P. Zic, Matthias S. Ikeda, Pierre Massat, Patrick M. Hollister, Linda Ye
| Summary:
Adiabatic decompression of para-quadrupolar materials has significant
potential as a cryogenic cooling technology. We focus on TmVO$_4$, an
archetypal material that undergoes a continuous phase transition to a
ferroquadrupole-ordered state at 2.15 K. Above the phase transition, each Tm
ion contributes an entropy of $k_B ln{2}$ due to the degeneracy of the crystal
electric field groundstate. Owing to the large magnetoelastic coupling, which
is a prerequisite for a material to undergo a phase transition via the
cooperative Jahn-Teller effect, this level splitting, and hence the entropy,
can be readily tuned by externally-induced strain. Using a dynamic technique in
which the strain is rapidly oscillated, we measure the adiabatic elastocaloric
coefficient of single-crystal TmVO$_4$, and thus experimentally obtain the
entropy landscape as a function of strain and temperature. The measurement
confirms the suitability of this class of materials for cryogenic cooling
applications, and provides insight to the dynamic quadrupole strain
susceptibility.
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