Rare earth single-molecule magnets make hard disks more powerful
Reporters learned from Xi'an Jiaotong University on the 10th that Professor Zheng Yanzhen of the Institute of Frontier Science and Technology of Xi'an Jiaotong University, in cooperation with Dr. Chilton of Manchester University, has made an important breakthrough in the study of the mechanism of single-molecule information storage, pointing out a new direction for the synthesis of single-molecule magnets that can be used at room temperature. Published in the international authoritative journal Nature Newsletter.
Single-molecule magnets are a new type of nano-magnetic materials with single molecule as magnetic unit, which exhibit the coexistence of classical magnetic relaxation and magnetic quantum tunneling. They have very unique physical and chemical properties and have broad application prospects in the fields of new materials and information carriers for the future. However, due to the very small size of molecules, the magnetic relaxation of these materials is greatly affected by the quantum tunneling effect. How to overcome the quantum tunneling effect and prevent information loss is a major obstacle in the field of single molecule information storage.
To solve this problem, a rare earth based single molecule magnet with special symmetry has been synthesized. The single molecule magnet exhibits an excellent linear Obah relaxation process at high temperatures, so it is suitable for studying quantum tunneling at lower temperatures. Using diamagnetic dilution, researchers found that the internal field has dual effects on quantum tunneling effect: when the external magnetic field is insufficient to suppress the quantum tunneling effect, the internal field can slow down the quantum tunneling process, but the internal field will lead to the quantum tunneling gap of rare earth ions, resulting in quantum tunneling effect. In order to verify the effect of hyperfine splitting on the quantum tunneling process, the effect of hyperfine splitting on the properties of single-molecule magnets of the compound was studied by replacing natural rare earth ions with non-nuclear spin rare earth isotopes. It was found that the hyperfine interaction generated by nuclear spin could open the tunneling gap, but it did not. It is not the main factor leading to the strong quantum tunneling effect under zero field, thus pointing to another possible culprit of the large number of sub-tunneling effects of rare earth ions, i.e. the vibration of molecules themselves. Based on this deduction, the quantum tunneling gap of this compound is analyzed for the first time, which is about 0.00001-0.0001 wave number. It is proposed that the reduction of molecular vibration can effectively suppress the quantum tunneling effect, which has important enlightenment significance in guiding the synthesis of room temperature single molecule magnets in the future.