Spin excitations in the quantum dipolar magnet Yb(BaBO${}_3$)${}_3$

Abstract

We report results of magnetization, specific-heat and muon-spin relaxation measurements on single crystals of disorder-free Yb${}^{3+}$ triangular lattice Yb(BaBO${}_3$)${}_3$. The magnetization experiments show anisotropic magnetic properties with Curie-Weiss temperatures $\hat{I}{¸}_{\perp }=-1.40$~K ($H\perp c$) and $\hat{I}{¸}_{\parallel }=-1.16$~K ($H\parallel c$) 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 $\hat{I}{¼}_{0}H>0.7$~T. At zero field, the increase of both $C_{\mathrm{mag}}/T$ and the muon spin relaxation rate $\hat{I}»$ below 1~K is due to the electronic spin excitations, which often exist in quantum magnets where dipole-dipole interaction creates an anisotropy of magnetic properties. The spin excitation is also supported by the unusual maximum of field dependence of $\hat{I}»$ due to the field-induced increase of the density of excitations. We argue that dipolar interaction is dominant and induces the spin dynamics in the quantum magnet Yb(BaBO${}_3$)${}_3$.

accepted by Phys. Rev. B