HoB₄ at high pressure and low temperature: an experimental and theoretical study

Abstract

Single crystals of HoB₄ have been grown and used for synchrotron X-ray diffraction studies at pressures up to 23 GPa and temperatures down to 100 K. The experimental bulk modulus 195±6 GPa is in good agreement with 188.4 and 198.2 GPa values calculated in the LSDA and LSDA+U approximations, indicating that mainly the boron sublattice determines the bulk modulus. The experimental c/a ratio decreases slightly with pressure, but the effect is small. An orthorhombic distortion begins at T _c≈ 295 K, i.e. at a temperature much higher than the Néel temperature T _N1=7.1 K. The behavior is interpreted in terms of built-in strains and crystal mosaicity.

Keywords:

• X-ray diffraction
• crystal structure
• equation of state
• density functional theory

Acknowledgements

We thank HASYLAB-DESY for permitting us to use the synchrotron radiation facility. L.G. and J.S.O. gratefully acknowledge the financial support from the Danish Natural Sciences Research Council through DANSCATT.