Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method

Details Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method

2011-12-06

arxiv.org/abs/1112.1362v1

Physics

Chemical Physics

15 pages, 1 figure, 3 tables

Scientific paper

Estimates of the exchange interaction parameter (J) between electronic magnetic momenta residing in the d-shells of several divalent first row transition metal ions, and those residing on the [TCNE]$^-$. anion-radicals (TCNE = tetracyanoethylene) that are bonded to the metal ion are obtained by the use of the EHCF method in the cluster approximation. The clusters geometry was set according to that observed for Mn$^{II}$(TCNE)$_{1/2}$(I$_3$)$_{1/2}$ and M$^{II}$(TCNE)(C$_4$(CN)$_8$)$_{1/2}$ (M = Fe, Mn) with the [TCNE]$^{-.}$. For the Mn$^{II}$(TCNE)$_{1/2}$(I$_3$)$_{1/2}$ two cluster types are considered: one with the geometry corresponding to [TCNE]$^{-.}$ in the two-dimensional layer, and another connecting the layers. For M$^{II}$(TCNE)(C$_4$(CN)$_8$)$_{1/2}$ only the layer position of the [TCNE]$^{-.}$ is considered. In all cases the LUMO (singly filled in the material) is predominantly concentrated on the ethylenic C-C bond and is antibonding. The J value for the Mn$^{II}$(TCNE)$_{1/2}$(I$_3$)$_{1/2}$ layer is at least as twice as strong as one for the similar geometry for M$^{II}$(TCNE)(C$_4$(CN)$_8$)$_{1/2}$. The correct order of magnitude of the calculated exchange parameters, as compared with those extracted from experimentsindicates the general validity of this approach. However, the direct comparison of these J values with the critical temperatures is not possible since these latter heavily depend on details of the interlayer coupling not available through the EHCF procedure. In order to get more information on the geometry dependence of the exchange parameters, the dependence on the tilt angle of the TCNE with respect to the plane formed by the metal ions and four equatorial NCMe groups was investigated. In all cases, a remarkably strong dependence, having different trends depending on the number of electrons in the d-shells of respective transition metal ions was observed.

Affiliated with

Also associated with

No associations

Rating

Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Exchange Parameters in the TCNE-based Magnets as Estimated with use of the Effective Hamiltonian Crystal Field Method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-381701