Observation of two types of magnetization relaxation in a weakly correlated antiferromagnetic chain of Mn(III)2 single-molecule magnets.

ABSTRACT

A Mn(III)(2)Fe(II) chain with a [-Mn(III)-(O(Ph))(2)-Mn(III)-ON-Fe(II)-NO-] repeat unit was synthesized via the assembling reaction of Mn(III) salen-type dimers and Fe(II) pyridyloximate complexes, where the -(O(Ph))- and -ON- bridges represent a biphenolate bridge and an oximate bridge, respectively. The bulky counter anions, BPh(4)(-), which surround the chain to form a zeolite-like brick wall, successfully isolate the chains from a magnetic point of view. This compound is isostructural with Mn(2)Ni-BPh(4), which is an SCM with S(T) = 3 (H. Miyasaka, A. Saitoh, M. Yamashita and R. Clérac, Dalton Trans., 2008, 2422). Because the Fe(II) unit is diamagnetic, the Mn(III) dimer, which has the potential to be a single-molecule magnet (SMM), is nearly magnetically isolated, although a weak antiferromagnetic interaction with J/k(B)≈-0.1 K is perturbed between the Mn(III) dimers with S(T) = 4 via the Fe(II) unit. Ac susceptibility data shows that two types of relaxation of the magnetization are present, which are attributed to SMM and chain relaxations.