English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Cobalt pyrochlore fluoride NaCaCo$_2$F$_7$ is a disordered frustrated magnetcomposed of Co$^{2+}$ ions with an effective spin-$\frac{1}{2}$ magnetic momentand exhibits spin freezing below $T_f \sim$2.4 K. We perform ultrasoundvelocity measurements on a single crystal of the cubic NaCaCo$_2$F$_7$. Thetemperature dependence of the bulk modulus (the breathing elastic mode)exhibits Curie-type softening upon cooling below $\sim$20 K down to $T_f$,which is suppressed by the magnetic field. This Curie-type softening should bea precursor to the enhancement of the strength of exchange disorder via thespin-lattice coupling, which causes the spin freezing. In contrast to themagnetic-field-suppressed Curie-type softening in the bulk modulus, thetrigonal shear modulus exhibits softening with a characteristic minimum uponcooling, which is enhanced by the magnetic field at temperatures below $\sim$20K. This magnetic-field-enhanced elastic anomaly in the trigonal shear modulussuggests a coupling of the lattice to the dynamical spin-cluster state. ForNaCaCo$_2$F$_7$, the observed elastic anomalies reveal an occurrence ofmagnetic-field-induced crossover from an isostructural lattice instabilitytoward the spin freezing to a trigonal lattice instability arising from theemergent dynamical spin-cluster state.

Softening of breathing elastic mode and trigonal elastic mode in disordered pyrochlore magnet NaCaCo$_2$F$_7$