Density functional investigation of why Ba2BiFeS5 and Ba2SbFeS5 differ in their magnetic properties

We examined the cause for the difference in the magnetic properties of the isostructural/isoelectronic compounds Ba2SbFeS5 and Ba2BiFeS5 by evaluating their spin exchange parameters on the basis of density functional theory calculations. The difference is traced to the exchange triangle made up of three strongly antiferromagnetic spin exchange paths, which exhibits stronger spin frustration for Ba2SbFeS5 than for Ba2BiFeS5.