Abstract
Resistivity, magnetic susceptibility, neutron scattering, and x-ray crystallography measurements were used to study the evolution of magnetic order and crystallographic structure in single-crystal samples of the BaSrFeAs and SrCaFeAs series. A nonmonotonic dependence of the magnetic ordering temperature on chemical pressure is compared to the progression of the antiferromagnetic staggered moment, characteristics of the ordering transition, and structural parameters to reveal a distinct relationship between the magnetic energy scale and the tetrahedral bond angle, even far above . In SrCaFeAs, an abrupt drop in precisely at the Ca concentration where the tetrahedral structure approaches the ideal geometry indicates a strong coupling between the orbital bonding structure and the stabilization of magnetic order, providing strong constraints on the nature of magnetism in the iron-arsenide superconducting parent compounds.
- Received 23 February 2012
DOI:https://doi.org/10.1103/PhysRevB.86.060504
©2012 American Physical Society