Magnetic ground state of the one-dimensional ferromagnetic chain compounds M(NCS)(2)(thiourea)(2) (M = Ni, Co)

Journal article

The magnetic properties of the two isostructural molecule-based magnets - Ni(NCS)2(thiourea)2, S=1 [thiourea=SC(NH2)2] and Co(NCS)2(thiourea)2, S=3/2 - are characterized using several techniques in order to rationalize their relationship with structural parameters and to ascertain magnetic changes caused by substitution of the spin. Zero-field heat capacity and muon-spin relaxation measurements reveal low-temperature long-range ordering in both compounds, in addition to Ising-like (D<0) single-ion anisotropy (DCo∼-100 K, DNi∼-10 K). Crystal and electronic structure, combined with dc-field magnetometry, affirm highly quasi-one-dimensional behavior, with ferromagnetic intrachain exchange interactions JCo≈+4 K and JNi∼+100 K and weak antiferromagnetic interchain exchange, on the order of J′∼-0.1 K. Electron charge- and spin-density mapping reveals through-space exchange as a mechanism to explain the large discrepancy in J-values despite, from a structural perspective, the highly similar exchange pathways in both materials. Both species can be compared to the similar compounds MCl2(thiourea)4, M = Ni(II) (DTN) and Co(II) (DTC), where DTN is known to harbor two magnetic-field-induced quantum critical points. Direct comparison of DTN and DTC with the compounds studied here shows that substituting the halide Cl- ion for the NCS- ion results in a dramatic change in both the structural and magnetic properties.

Authors: Curley, SPM; Scatena, R; Williams, RC; Goddard, PA; Macchi, P

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review Materials
• Volume: 5
• Issue: 3
• Article number: 34401
• Publication date: 2021-03-03
• Acceptance date: 2021-02-03
• DOI: 10.1103/PhysRevMaterials.5.034401
• EISSN: 2475-9953
• ISSN: 2475-9953
• Language: English
• Keywords: FFR