We present a comprehensive experimental investigation of Yb magnetic dimers in Yb0.04Y0.96AlO3, an Yb-doped Yttrium Aluminum Perovskite (YAP) 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≈0.2~meV 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 intra-dimer 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 [arXiv:1904.11513, arXiv:1902.04112], and in contrast to Yb2Pt2Pb [arXiv:1606.01309, arXiv:1907.01067]. The obtained results are precisely reproduced by analytical calculations for the Yb dimers.
@article{arxiv.2004.07325,
title = {Experimental observation of magnetic dimers in diluted Yb:YAlO$_3$},
author = {S. E. Nikitin and Tao Xie and A. Podlesnyak and I. A. Zaliznyak},
journal= {arXiv preprint arXiv:2004.07325},
year = {2020}
}