JAPAN NANONET BULLETIN - 7th Issue - December 11, 2003

YOUNG RESEARCHERS’ INTRODUCTION

Hitoshi MIYASAKA Assistant Professor, Department of Chemistry, Tokyo Metropolitan University Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) 1993 Graduated from Department of Chemistry, Shimane University 1998 Ph.D. , Kyushu University Joined the group of Prof. Susumu Kitagawa at Kyoto University and then the group of Prof. Kim R. Dunbar at Texas A&M University, USA. 2000 Assistant Professor, Tokyo Metropolitan University 2001 Researcher (Joint Appointment), “Structural Ordering and Physical Properties”, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) E-mail address:

Hitoshi MIYASAKA,
Assistant Professor, Department of Chemistry, Tokyo Metropolitan University
Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST)

Controls of structural ordering and magnetism for single-chain magnets

The origin of bulk magnets lies in the cooperative phenomena of ordering spins in three dimensions. One-dimensional spin arrangement, which is magnetically isolated in a three-dimensional sphere, does not allow the formation of bulk magnets. However, a kind of metastable magnet known as a single chain magnet (SCM) behaves similarly to superparamagnets. To design this type of system, three essential factors must be considered.

First, spin carriers must exhibit a strong uniaxial anisotropy to be able to block or “freeze” their magnetization in one direction. The material must also exhibit a spontaneous magnetization to be called a magnet. Therefore, individual magnetic moments in the chain must not cancel out in the “frozen” state. Finally, chains must be isolated magnetically as much as possible to avoid three-dimensional ordering. Here, the aim of our project is to construct such single chain magnets based on metal complexes.

Recently, we reported on an SCM of a heterometallic one-dimensional system of Mn^Ⅲ and Ni^Ⅱions: [Mn(saltmen)]2[Ni(pao)2(py)2](ClO4)2 (saltmen^2- = N,N’ – (1,1,2,2-tetramethylethylene) bis(salicylideneiminate) and pao^- = pyridine-2-aldoxime) (Figure 1). The compound exhibited a slow relaxation of magnetization obeying the Debye model with a single relaxation process (Figure 2).

Fig. 1 Large Image Packing diagrams of a Single-Chain Magnet, Mn2(saltmen)2Ni(pao)2(py)2](PF6)2. a) The projection in the ac plane, the chains running on this plane (the counter anions are omitted for clarity). b) The projection along the chain, the counter anions locating between the chains. The nearest interchain metallic distance is over 10.3 Å.

Fig. 2 Cole-Cole plot and frequency dependence of ac susceptibility.