Abstract
The magnetism of magnetoelectric pyroxenes and is studied by density functional theory calculations, quantum Monte Carlo (QMC) simulations, neutron diffraction, as well as low- and high-field magnetization measurements. In contrast with earlier papers, we find that the two compounds feature remarkably different, albeit nonfrustrated magnetic models. In , two relevant exchange integrals, K along the structural chains and K between the chains, form a two-dimensional anisotropic honeycomb lattice. In contrast, the spin model of is constituted of three different exchange couplings. Surprisingly, the leading exchange K operates between the chains, while K is about two times smaller. The additional interlayer coupling renders this model three dimensional. QMC simulations reveal excellent agreement between our magnetic models and the available experimental data. Underlying mechanisms of the exchange couplings, magnetostructural correlations, as well as implications for other pyroxene systems are discussed.
1 More- Received 6 February 2014
- Revised 22 October 2014
DOI:https://doi.org/10.1103/PhysRevB.90.214424
©2014 American Physical Society