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, Mossbauer 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 FeCl 2 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+Fe 3+O2 as a result of the increase in overlap of atomic orbitals.
- Electronic/magnetic transitions
- High pressure
- Strongly correlated systems
- X-ray crystallography