# Cobalt(II) Single‐Chain Magnet With Strong Anisotropy and Ferromagnetic IntraChain Coupling

## TL;DR

A new cobalt-based single-chain magnet shows record magnetic properties due to strong anisotropy and ferromagnetic coupling.

## Contribution

A clean, intrinsic design strategy for high-performance single-chain magnets using redox-active ligands is introduced.

## Key findings

- The SCM has an energy barrier of 560 K and blocking temperature of 21.5 K, the highest for SCM systems.
- Strong axial anisotropy and ferromagnetic exchange promote long-range spin correlation.
- A 1D-to-3D magnetic crossover is observed at low temperatures.

## Abstract

Co(II)‐based coordination polymer is reported as a new benchmark single‐chain magnet (SCM), exhibiting an energy barrier (U
eff) of 560 K and a blocking temperature (T
B) of 21.5 K‒both the highest values observed for SCM systems. The magnetic behavior originates from the synergistic balance between strong axial anisotropy (D
Co = –83 cm−1) and moderate ferromagnetic exchange (J
Co‐Co = +17.7 K), promoting long‐range spin correlation over thousands of magnetic ions. Detailed analysis of the correlation length and domain‐wall energy reveals a wide SCM regime and a 1D‐to‐3D magnetic crossover at low temperature. Unlike previously reported radical‐bridged SCMs, this work demonstrates a clean, intrinsic design strategy for realizing extreme single‐chain magnetism, offering new principles for developing robust molecular spin materials.

A new high‐performance single‐chain magnet (U
eff = 560 K) exhibits strong magnetic anisotropy and ferromagnetic intrachain interactions using redox‐active bridging ligands.