Spin excitations in the quantum dipolar magnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Yb</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>BaBO</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Abstract

We report results of magnetization, specific heat, and muon spin relaxation ($\ensuremath{\mu}\mathrm{SR}$) measurements on single crystals of disorder-free ${\mathrm{Yb}}^{3+}$ triangular lattice $\mathrm{Yb}{({\mathrm{BaBO}}_{3})}_{3}$. The magnetization experiments show anisotropic magnetic properties with Curie-Weiss temperatures ${\ensuremath{\theta}}_{\ensuremath{\perp}}=\ensuremath{-}1.40\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ ($H\ensuremath{\perp}c$) and ${\ensuremath{\theta}}_{\ensuremath{\parallel}}=\ensuremath{-}1.16\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ ($H\ensuremath{\parallel}c$) determined from low-temperature data. The absence of both long-range antiferromagnetic order and spin freezing is confirmed down to 0.27 K at zero field. A two-level Schottky anomaly due to the opening of the ground-state Kramers doublet is observed from the low-temperature specific heat measurements when the applied magnetic fields ${\ensuremath{\mu}}_{0}H&gt;0.7\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. At zero field, the increase of both ${C}_{\mathrm{mag}}/T$ and the muon spin relaxation rate $\ensuremath{\lambda}$ below 1 K is due to the electronic spin excitations, which often exist in quantum magnets where dipole-dipole interactions create an anisotropy of magnetic properties. The spin excitation is also supported by the unusual maximum of the field dependence of $\ensuremath{\lambda}$ due to the field-induced increase in the density of excitations. We argue that dipolar interaction is dominant and induces the spin dynamics in the quantum magnet $\mathrm{Yb}{({\mathrm{BaBO}}_{3})}_{3}$.

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