Influence of aging on the structure and magnetic properties of surface deposited single-molecule magnets

Single-molecule magnets (SMMs) are the new class of nanoscale materials with unique magnetic properties of purely molecular origin, which are particularly interesting in terms of applications in nanoelectronics. The realization of highly-performance nanoelectronic devices based on the manipulation of SMMs requires surface deposition of such entities. The organization of individual bistable magnetic molecules on the surface, however, demands the precise chemical method and searching of proper supporting material, since any changes at structure may influence on the magnetic properties. Moreover, for practical application it is important to follow the changes of SMMs magnetic performance with the time.

In such study we present a possibility for deposition of Mn₁₂-based SMMs on the surface of silica nanostructures with preservation of its structure and magnetic properties. The procedure was based on anchoring the individual SMMs onto the silica support using propyl carbonic acid groups. The performed spectroscopy analysis confirm correct anchoring of molecules on the surface while magnetic measurements show retaining of magnetic hysteresis and slow relaxation process after surface deposition. In order to analyze how the characteristics of such material change over long time period the aging effect was investigated. The aging studies revealed significant decrease in basic magnetic parameters (coercivity and remanence) and change in magnetic relaxation behavior. The Raman spectroscopy measurements revealed gradual degradation of the compound over time, which explain the observed magnetic changes. Also, the aged samples were compared with the as-synthesized material after thermal decomposition to check, if the structural modifications caused by the temperature, affect the similar way as aging process.