Single-molecule magnets (SMMs) can exhibit magnetic bistability at the molecular level, making them promising for high-density information storage. The relaxation time of SMMs in the absence of a magnetic field reflects their memory retention capabilities, and should be maximized for storage applications.
Intermolecular magnetic dipole interactions are common in magnetic molecule aggregates. However, they usually trigger rapid quantum tunneling of magnetization (QTM), resulting in information loss. Finding a way to utilize the inevitable dipole interaction in a beneficial way could turn this negative into a positive.
Jun-Liang Liu, Sun Yat-Sen University, Guangzhou, China, and colleagues have developed two SMMs with different supramolecular arrangements of magnetic dipoles: staggered and side-by-side (see below). The two complexes (common structural unit pictured above) were synthesized via a reaction of dysprosium salts, the planar ligand bis(thiosemicarbazone) ligand (2,6-diacetylpyridine)-bis(4-phenylthiosemicarbazone) (H2DABT), and the axial ligand 4-(tert-butyl)−2,6-di(1,3-dithiolan-2-yl)phenol (HtBu-DDTP) with either NEt3 or tetramethylguanidine (TMG). Using this approach, the team obtained [HNEt3][Dy(DABT)(tBu-DDTP)2]·2MeCN·H2O (staggered) and [HTMG][Dy(DABT)(tBu-DDTP)2]·3H2O (side-by-side).
The side-by-side complex exhibits a 104-fold slower zero-field relaxation time at 2 K than the staggered one. Intriguingly, the side-by-side complex also shows faster magnetic relaxation upon dilution. This provides evidence for the presence of aggregation-induced suppression of QTM in the side-by-side complex. The researchers suggest that aggregation-induced suppression of QTM could be an effective way to enhance the capabilities of non-volatile data storage without altering the molecular structure or lowering the storage density.
- Aggregation‐induced suppression of quantum tunneling by manipulating intermolecular arrangements of magnetic dipoles,
Wei Deng, Shan‐Nan Du, Ze‐Yu Ruan, Xiao‐Jun Zhao, Yan‐Cong Chen, Jun‐Liang Liu, Ming‐Liang Tong,