Strengthening the Magnetic Interactions in Pseudobinary First-Row Transition Metal Thiocyanates, M(NCS)2

• Published in: Inorganic chemistry 2020-08, Vol.59 (16), p.11627-11639
• Main Authors: Bassey, Euan N, Paddison, Joseph A. M, Keyzer, Evan N, Lee, Jeongjae, Manuel, Pascal, da Silva, Ivan, Dutton, Siân E, Grey, Clare P, Cliffe, Matthew J
• Format: Article
• Language: English
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c01478

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 t 2g 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.