Spin excitations in the quantum dipolar magnet Yb(BaBO3)3

Abstract

We report results of magnetization, specific heat, and muon spin relaxation (μSR) 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 θ ⊥ = −1.40 K (H ⊥ c) and θ = −1.16 K (H 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 μ 0 H > 0.7 T. At zero field, the increase of both C mag /T and the muon spin relaxation rate λ 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 λ 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 Yb(BaBO 3 ) 3 .

Adiabatic demagnetization cooling well below the magnetic ordering temperature in the triangular antiferromagnet KBaGd(BO3)2

“…It is further worth noting that the nearest-neighbor exchange coupling of 44 mK in KBaGd(BO 3 ) 2 is about three times larger than the dipolar coupling of 15 mK (dipole-dipole interaction energy of 186 mK assuming g = 2 and S = 7 2 ) expected between the Gd 3+ spins 7 2 in this crystal structure. By contrast, Yb 3+ borates with similar metal-metal distances of about 5.5 Å are usually dominated by dipolar couplings [16,25,26]. Therefore, the larger magnetic moment of Gd 3+ triggers an exchange component of the magnetic interaction, 104402-6 in addition to the dipolar one.…”