Abstract
We present a comprehensive experimental investigation of Yb magnetic dimers in Yb0.04Y0.96AlO3, an Yb-doped yttrium aluminum perovskite YAlO3, by means of specific heat, magnetization, and high-resolution inelastic neutron scattering (INS) measurements. In our sample, the Yb ions are randomly distributed over the lattice and ∼7% of Yb ions form quantum dimers due to nearest-neighbor antiferromagnetic coupling along the c axis. At zero field, the dimer formation manifests itself in an appearance of an inelastic peak at Δ≈0.2meV in the INS spectrum and a Schottky-like anomaly in the specific heat. The structure factor of the INS peak exhibits a cosine modulation along the L direction, in agreement with the c-axis nearest-neighbor intradimer coupling. A careful fitting of the low-temperature specific heat shows that the excited state is a degenerate triplet, which indicates a surprisingly small anisotropy of the effective Yb-Yb exchange interaction despite the low crystal symmetry and anisotropic magnetic dipole contribution, in agreement with previous reports for the Yb parent compound, YbAlO3 [L. Wu et al., Nat. Commun. 10, 698 (2019), L. S. Wu et al., Phys. Rev. B 99, 195117 (2019)], and in contrast to Yb2Pt2Pb [L. S. Wu et al., Science 352, 1206 (2016), W. J. Gannon et al., Nat. Commun. 10, 1123 (2019)]. The obtained results are precisely reproduced by analytical calculations for the Yb dimers.
