Universal link of magnetic exchange and structural behavior under pressure in chromium spinels

Abstract

We have conducted high-pressure X-ray diffraction studies on the MnCr 2 O 4 and NiCr 2 O 4 spinels at room temperature. Both compounds undergo pressure-induced structural transitions into diverse tetragonal modifications. Based on these experimental observations and our ab initio calculations, we show that the Cr-oxide spinels with magnetic A 2+ cations (A 2+ = Mn, Fe, Co, Ni) follow a similar trend as their chalcogenide counterparts with non-magnetic A 2+ ions, i.e. the transition pressure is proportionally related with the magnitude of the Cr-Cr magnetic exchange interactions. Therefore, we reach the conclusion that the Cr-Cr magnetic exchange interactions alone suffice to account for the high-pressure behavior of these systems. Our results clearly depict the close relationship between the structural and magnetic degrees of freedom in Cr-bearing spinels.

From Semiconducting to Metallic: Jahn–Teller-Induced Phase Transformation in Skyrmion Host GaV4S8

“…The errors in the fitting results come from the fitting process without including the propagation of uncertainties from pressure and volume. The bulk modulus of the cubic phase of this lacunar spinel compound is different from other conventional spinels, such as ZnGa 2 O 4 , ZnCr 2 Se 4 , CoCr 2 O 4 , CuCr 2 O 4 , ZnCr 2 S 4 , MnCr 2 O 4 , NiCr 2 O 4 , CdCr 2 Se 4 , and so on. The discrepancies are predominantly caused by the different crystal structures, F 4̅3 m versus Fd 3̅ m , in these two systems.…”

“…Like temperature, pressure is another controllable variable that can be externally altered to tune and probe the physical natures (lattice structure, optical, and electrical properties) of GaV 4 S 8 due to the strong coupling between lattice, electronic, and spin degrees of freedom in this compound . More interesting, whether the Jahn–Teller effect, which has been observed in GaV 4 S 8 at the cooling condition as well as in CuWO 4 , MnCr 2 O 4 , NiCr 2 O 4 , and ZnCr 2 S 4 under high pressure, is enabled to be induced by compression at room temperature in this compound. − However, the literature gives very limited information about the high-pressure behavior of GaV 4 S 8 ; , Even its crystal structure transformation under room temperature compression is unknown. In the present study, we used high-pressure synchrotron single crystal and powder X-ray diffraction to detect the delicate change in the crystal structure of this material under a broad pressure range from ambient to 60 GPa.…”

Spin reorientation by Ni doping in Cu1−Ni Cr2O4 spinels with x = 0 and 0.1, and evidence for canted magnetic Cr order above the onset of a ferromagnetic Cu

“…The origin of the orthorhombic distortion at the low temperature transition is associated either with the spin ordering of the Cu/Ni ions alone, or with the formation of the ferrimagnetic structure involving CrF as well. Although our measurements do not allow inferring magnetic exchange constants, they can provide a fruitful testing ground for DFT calculations, which predict exchange constants [27].…”

Mg-Doped CoCr2O4 Nanoparticles: Implications for Magnetic Memory and Magnetocaloric Effect

“…For values of 8/9 < u < 1.298, an antiferromagnetic (AFM) ferrimagnetic (FIM) spiral configuration is indicated. On the other hand, u > 1.298 signifies an unstable spiral state …”