An Ising iron(ii) chain exhibits a large finite-size energy barrier and "hard" magnetic behaviour.

One-dimensional spin chains featuring strong axial anisotropic magnetism are promising candidates for isolatable and miniatured information storage materials, the so-called single-chain magnets (SCMs). Here we show a mixed azido/carboxylato bridged metamagnetic iron(II) chain [Fe(N-3)(2)(4-mpc)](n) (4-mpc = N-methylpyridinium-4-carboxylate) with a large energy barrier of 150 K, a large remnant magnetization (1.55N beta) and coercivity (1.7 T at 2 K) for homo-spin SCMs. Heat capacity and Mossbauer spectroscopy studies corroborate the intrinsic nature of SCM behavior regardless of weak interchain magnetic interactions, which lead to the coexistence of metamagnetism but not long-range magnetic ordering. Moreover, detailed magnetic investigations indicate that the system is not only within the " Ising limit " but also in the " finite-size " regime.