Crystallographic transitions related to high-pressure magnetic and electronic phenomena in Fe-based compounds

Abstract

The main purpose of this paper is to address the issue of crystallographic transitions related to magnetic/electronic phenomena in strongly correlated transition metal (TM) compounds in a regime of very high static density. The experimental tools used were: synchrotron X-ray diffraction, Mössbauer spectroscopy and electrical resistivity. We focus on the following cases: (i) high-spin to low-spin transition which could lead to a significant reduction of the TM ionic radii and therefore even a structural transition; (ii) sluggish structural phase transitions in antiferromagnetic insulators FeI₂ and FeCl₂ attributed to the onset of a Mott transition; (iii) volume dependence of the orbital term of the moment in FeI₂ and FeCl₂ resulting in its eventual collapse, which is accompanied by a significant lattice distortion; and (iv) pressure-induced metal–metal intervalence charge transfer in the antiferromagnetic Cu¹⁺Fe³⁺O₂ as a result of the increase in overlap of atomic orbitals.

Keywords:

• high pressure
• strongly correlated systems
• X-ray crystallography
• electronic/magnetic transitions

Acknowledgements

We would like to thank Drs G.R. Hearne, R. Jeanloz, R.D. Taylor, and A. Kurnosov for fruitful discussions and contributions to the XRD and MS experiments. We thank O. Naaman, G.Yu. Machavariani, M. Kertser, and E. Greenberg for assisting with the synchrotron experiments and for performing the resistivity measurements. We thank Drs T. Le Bihan and S. Carlson for experimental assistance with the facilities of the ID30 HP beam at ESRF. This work was supported in part by ISF Grant No. 36/05.

Notes

^†Structural transitions related to magnetic phenomena.