Autori: M. Ferbinteanu, H. Miyasaka, W. Wernsdorfer, K. Nakata, K. Sugiura, M. Yamashita, C. Coulon, and R. Clerac

Editorial: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 127, p.3090-3099, 2005.

Rezumat:

(NEt4)[Mn2(5-MeOsalen)2Fe(CN)6] (5-MeOsalen2- = N, N’-ethylenebis(5-methoxysalicylideneiminate)) is a heterometallic one-dimensional assembly made of the trinuclear [MnIII(SB)-NC-FeIII-CN-MnIII(SB)] (SB is a salen-type Schiff-base ligand). The compound has two types of bridges, a cyano bridge (-NC-) and a biphenolate bridge (-(O)2-), connecting MnIII and FeIII ions and the two MnIII ions,
respectively. Both bridges mediate ferromagnetic interactions, as shown by modeling the magnetic susceptibility above 10 K. The dc magnetic measurements of a single crystal using micro-SQUID and Hall-probe magnetometers revealed a uniaxial anisotropy with an easy axis lying along the chain direction. Frequency dependence of the ac susceptibility and time dependence of the dc magnetization have been performed to study the slow relaxation of the magnetization. A mean relaxation
time has been found, and its temperature dependence has been studied. Above 1.4 K, both magnetic
susceptibility and relaxation time are in agreement with the dynamics described in the 1960s by R. J.
Glauber for one-dimensional systems with ferromagnetically coupled Ising spins. As expected, at lower temperatures below 1.4 K, the relaxation process is dominated by the finite-size chain effects. The detailed analysis of this single-chain magnet behavior and its two regimes is consistent with magnetic parameters independently estimated and allows the determination of the average chain length. This work illustrates nicely a new strategy to design single-chain magnets by coupling ferromagnetically single-molecule magnets in one dimension.

Cuvinte cheie: Single Chain Magnets; Slow Relaxation of the Magnetization; Ferromagnetric Coupling; Magnetic Anisotropy