Coercive Fields Above 6 T in Two Cobalt(II)–Radical Chain Compounds

• Published in: Angewandte Chemie International Edition Vol. 59; no. 26; pp. 10610 - 10618
• Main Authors: Liu, Xiaoqing, Feng, Xiaowen, Meihaus, Katie R., Meng, Xixi, Zhang, Yuan, Li, Liang, Liu, Jun‐Liang, Pedersen, Kasper S., Keller, Lukas, Shi, Wei, Zhang, Yi‐Quan, Cheng, Peng, Long, Jeffrey R.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.06.2020
• Edition: International ed. in English
• Subjects: Chains; Cobalt; coercive field; Computer applications; Crystallography; Hysteresis; Industrial engineering; Magnetic fields; magnetic hysteresis; Magnetic materials; magnetism; molecular magnetism; Nanotechnology; Nitroxide; Permanent magnets; Rare earth elements; single-chain magnets; magnetism; molecular magnetism; magnetic hysteresis; coercive field; single-chain magnets
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202002673

Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide‐free hard magnets. Zero‐ and one‐dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom‐up nature of their synthesis. Here, we present two one‐dimensional cobalt(II) systems Co(hfac)2(R‐NapNIT) (R‐NapNIT=2‐(2′‐(R‐)naphthyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide, R=MeO or EtO) supported by air‐stable nitronyl nitroxide radicals. These compounds are single‐chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three‐dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry. High‐coercivity one‐dimensional magnets: Novel cobalt(II)‐nitronyl nitroxide radical chains featuring crystallographically determined alternating magnetic sublattices exhibit exceptional magnetic hardness and coercive fields up to 65 kOe.