Abstract
Understanding the effect of chemical composition on the strength of magnetic interactions is key to the design of magnets with high operating temperatures. The magnetic divalent first-row transition metal (TM) thiocyanates are a class of chemically simple layered molecular frameworks. Here, we report two new members of the family, manganese(II) thiocyanate, Mn(NCS)2, and iron(II) thiocyanate, Fe(NCS)2. Using magnetic susceptibility measurements on these materials and on cobalt(II) thiocyanate and nickel(II) thiocyanate, Co(NCS)2 and Ni(NCS)2, respectively, we identify significantly stronger net antiferromagnetic interactions between the earlier TM ions-a decrease in the Weiss constant, θ, from 29 K for Ni(NCS)2 to-115 K for Mn(NCS)2-a consequence of more diffuse 3d orbitals, increased orbital overlap, and increasing numbers of unpaired t2g electrons. We elucidate the magnetic structures of these materials: Mn(NCS)2, Fe(NCS)2, and Co(NCS)2 order into the same antiferromagnetic commensurate ground state, while Ni(NCS)2 adopts a ground state structure consisting of ferromagnetically ordered layers stacked antiferromagnetically. We show that significantly stronger exchange interactions can be realized in these thiocyanate frameworks by using earlier TMs.
| Original language | English |
|---|---|
| Pages (from-to) | 11627-11639 |
| Number of pages | 13 |
| Journal | Inorganic Chemistry |
| Volume | 59 |
| Issue number | 16 |
| DOIs | |
| State | Published - Aug 17 2020 |
Funding
E.N.B. thanks the EPSRC for financial support. J.A.M.P.’s work at Cambridge was supported by Churchill College, University of Cambridge. J.A.M.P.’s work at Oak Ridge National Laboratory (ORNL) was supported by the Laboratory Directed Research and Development Program of ORNL, managed by UT-Battelle, LLC for the US Department of Energy (discussion of magnetic modelling) and the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (computational resources). E.N.K. thanks NSERC of Canada for a PGSD. J.L. thanks Trinity College, University of Cambridge for financial support. M.J.C. acknowledges the School of Chemistry, University of Nottingham for a Hobday Fellowship. Magnetic measurements were carried out using the Advanced Materials Characterisation Suite, funded by EPSRC Strategic Equipment Grant EP/M000524/1. We also acknowledge the Rutherford Appleton Laboratory for access to the ISIS Neutron Source.
| Funders | Funder number |
|---|---|
| ORNL Laboratory Research and Development Program | |
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering | |
| Engineering and Physical Sciences Research Council | |
| Trinity College, University of Cambridge | |
| Churchill College, University of Cambridge | |
| School of Chemistry, University of Nottingham | EP/M000524/1 |