Constrained DFT+ approach for understanding the magnetic behaviour of ACrO (A=Zn, Mg, Cd and Hg) compounds
arXiv:1607.07225 · doi:10.1016/j.physleta.2017.01.002
Abstract
In this work, we try to understand the inconsistency reported by [Yaresko, Phys. Rev. B. {\bf 77}, 115106 (2008)] in the theoretically estimated nature and the variation of magnitude of nearest neighbour exchange coupling constant ($\arrowvert${\it J}$\arrowvert$) with increasing in ACrO (A=Zn, Cd, Mg and Hg) compounds by using density functional theory. In unconstrained calculations, the nature and variation of $\arrowvert${\it J}$\arrowvert$ as a function of in the present study are not consistent with the experimental data and not according to the relation, {\it J} especially for CdCrO and HgCrO for 3 eV and U=2-6 eV, respectively. Such an inconsistent behavior of $\arrowvert${\it J}$\arrowvert$ is almost similar to that of Yaresko for these two compounds for =2-4 eV. For ZnCrO and MgCrO, the nature and the variation of $\arrowvert${\it J}$\arrowvert$ in the present work are in accordance with the experimental data and above mentioned relation for =2-6 eV and are similar to that of Yaresko for ZnCrO for =2-4 eV. However, in constrained calculations the nature and variation of $\arrowvert${\it J}$\arrowvert$ in the present work are according to experimental data and above above mentioned relation for all four compounds. Hence, the present study shows the importance of constrained calculations in understanding the magnetic behaviour of these spinels. The values of magnitude of Curie-Weiss temperature [$\arrowvert$()$\arrowvert$] for ZnCrOMgCrOCdCrOHgCrO for =2-5 eV, which are according to the order of experimentally observed values for these spinels.
16 pages, 3 figures, 2 tables