Crystal-field potential and short-range order effects in inelastic neutron scattering, magnetization, and heat capacity of the cage-glass compound HoB12

The strongly correlated system $\mathrm{Ho}¹¹\mathrm{B}₁₂$ with boron sublattice Jahn-Teller instability and nanoscale electronic phase separation (dynamic charge stripes) was studied in detail by inelastic neutron scattering (INS), magnetometry, and heat capacity measurements at temperatures in the range of 3--300 K. From the analysis of registered INS spectra, we determined parameters of the cubic crystal field (CF) at holmium sites ${B}₄=\ensuremath{-}0.333$ meV and ${B}₆=\ensuremath{-}2.003$ meV (in Stevens notations), with an unconventional large ratio ${B}₆/{B}₄$ pointing to the dominant role of conduction electrons in the formation of a CF potential. The molecular field in the antiferromagnetic (AFM) state ${B}_{\mathrm{loc}}=(1.75\ifmmode\pm\else\textpm\fi{}0.1)$ T has been directly determined from the INS spectra together with short-range order effects detected in the paramagnetic state. A comparison of measured magnetization in diluted ${\mathrm{Lu}}_0.99{\mathrm{Ho}}_0.01{\mathrm{B}}₁₂$ and concentrated ${\mathrm{HoB}}₁₂$ single crystals showed a strong suppression of Ho magnetic moments by AFM exchange interactions in holmium dodecaboride. To account explicitly for the short-range AFM correlations, a self-consistent holmium dimer model was developed that allowed us to reproduce successfully field and temperature variations of the magnetization and heat capacity in the cage-glass phase of ${\mathrm{HoB}}₁₂$ in external magnetic fields.