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

TL;DR

This study investigates the crystal field effects, magnetic interactions, and short-range order in HoB12 using neutron scattering, magnetometry, and heat capacity measurements, revealing the dominant role of conduction electrons and antiferromagnetic correlations.

Contribution

It provides detailed parameters of the crystal field, measures the molecular field, and introduces a holmium dimer model to explain magnetic and thermal properties of HoB12.

Findings

Determined crystal field parameters B4 and B6 with an unconventional ratio.

Measured the molecular field in the antiferromagnetic state as approximately 1.75 T.

Developed a holmium dimer model that reproduces magnetization and heat capacity behavior.

Abstract

The strongly correlated system Ho11B12 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 3-300 K. From the analysis of registered INS spectra, we determined parameters of the cubic crystal field at holmium sites, B4=- 0.333 meV and B6= -2.003 meV (in Stevens notations), with an unconventional large ratio B6/B4 pointing on the dominant role of conduction electrons in the formation of a crystal field potential. The molecular field in the antiferromagnetic state, Bloc = (1.75+- 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 Lu0.99Ho0.01B12 and concentrated HoB12 single crystals showed a strong suppression of Ho magnetic moments by antiferromagnetic exchange interactions in holmium dodecaboride. To account explicitly for the short-range antiferromagnetic 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 HoB12 in external magnetic fields.