Recently, a research team identified two possible magnetic interaction images in Sr 2 IrO 4 , which marked a new progress in the magnetic superexchange coupling study in Sr 2 IrO 4 5d associative system.
The team was led by Dr. ZHANG Guoren from Institute of solid State Physics (ISSP), Hefei Institutes of Physical Science (HFIPS) , Chinese Academy of Sciences, in collaboration with researchers from Jülich Research Centre, Germany.
"We studied the magnetic couplings in Sr 2 IrO 4 in the Mott-insulating picture by combing different theories” said ZHANG Guoren, “and identified two possible scenarios of them.”
They studied the magnetic interactions in the strong-to-intermediate coupling regime. The superexchange pseudospin tensors was calculated up to fourth order, and their dependence on the screened Coulomb interaction integrals U and J and crystal-field splitting was analyzed. Due to term cancellations, the experimental nearest-neighbor coupling is reasonably well reproduced for a whole range of realistic values.
They identified a phenomenon. The increasing Hund’s rule coupling J could lead to large fourth-order contributions. That’s why the ferromagnetic next-nearest-neighbor coupling extracted from the spin-wave dispersion.
This regime is characterized by a sizable ring exchange K. For (U,J) values that yield a Mott insulator with a half-filled jeff =1/2 state, but fourth-order terms remain minor even if the gap is small.
"The electronic properties of Sr 2 IrO 4 and La 2 CuO 4 are similar,” said ZHANG, “so it can help us to understand the mechanism for superconductivity in doped La 2 CuO 4 ."
This work could also shed light on the correct modelization for other systems, such as the bilayer Sr 3 Ir 2 O 7.
The relevant findings were published in Physical Review B .
Link to paper: Magnetic superexchange couplings in Sr2IrO4
Physical Review B
Experimental study
Not applicable
Magnetic superexchange couplings in Sr 2 IrO 4
13-Sep-2021