Magnetoelectric coupling: making single-molecule magnets more "obedient"
Whether it's a smart phone with you or a supercomputer deployed in the computer room, having more storage space and capacity is their common technology "dream." With the deepening of material research, single-molecule magnets have also emerged as the times require, and the use of single-molecule magnets as information storage units to achieve ultra-high-density information storage has become a goal that scientists are striving for.
Since the first single-molecule magnet Mn12 was first discovered in 1993, the magnetoelectric properties of single-molecule magnets have been deepened. Recently, researchers from the Institute of Physics of the Chinese Academy of Sciences and Nankai University have observed significant magnetic-dielectric effects for the first time in a single-molecule magnet containing rare earth ions (Dy). A few days ago, the reporter interviewed Dr. Wang Yuxia, one of the experimenters and the Department of Chemistry of Nankai University, and listened to her telling the wonderful process of how the electric field can make the single-molecule magnet "obedient" and magnetically regulate it.
Big "belly" - with more data storage capacity
A single-molecule magnet is a special type of magnet composed of discrete, non-magnetically interacting nano-sized molecular units. Each molecule is an independent magnetic functional unit that exhibits superparamagnetism at high temperatures and appears at low temperatures. Hysteresis and magnetization quantum tunneling behavior.
Wang Yuxia told the Science and Technology Daily that the magnetic properties of ordinary magnets are mainly derived from the magnetic interaction between adjacent paramagnetic centers. Due to the size relationship, nano-magnetic particles will produce some special quantum behavior. A single-molecule magnet can be switched between two states of "0" (molecular orientation in the direction of the magnetic field) and "1" (the direction of the molecular orientation in the reverse magnetic field) like a tiny magnet. "It is this feature that gives single-molecule magnets a large 'thorage' that can greatly increase the information storage density, meaning that storage devices made from such magnets have greater data storage capabilities." Wang Yuxia said, " Single-molecule magnet technology can store more than 200 megabits of data per square inch (6.45 square centimeters), and it is expected to achieve ultra-high-density information storage if applied to quantum computers in the future."
Have "personality" - maybe "sneak out"
Magnetics and electricity are two basic properties of matter. As early as more than 100 years ago, scientists such as Maxwell unified magnetism and electricity in the framework of electrodynamics. Scientists have been trying to explore the coupling of magnetic and electrical properties in solids. Regulation.
The Book of Songs has a cloud that "put me to papaya and report it to Joan". Scientists have been hoping to see this "harmonious" electromagnetic coupling scene on single-molecule magnets. Wang Yuxia told reporters that the magnetic behavior of single-molecule magnets is manifested by the slow magnetic relaxation of a single molecule. "The so-called relaxation, in layman's terms, is time." Seeing the reporter's face ignorant, Wang Yuxia explained, "It is like a person who is over the mountains, a single-molecule magnet exhibits magnetic behavior, and its electrons also pass through a high slope. While climbing to the other side, usually this will take some time. This time is relaxation.” The reporter learned that due to the high energy levels of rare earth elements, the electrons of single-molecule magnets may “sneak out”. "The straight line passes through, so that the energy consumption from side to side is less, and the relaxation time is shorter. "These are not conducive to the magnetic properties of single-molecule magnets." Wang Yuxia said, "Our research hopes to better balance the 'personality' of single-molecule magnets and achieve effective and reversible regulation of magnetism through electric fields."
This orderly controllable magnetoelectricity means high conversion efficiency and also means considerable application prospects. "For example, in magnetic storage, magnetic recording has a fast reading speed and slow writing, and ferroelectric recording is complicated to read and write fast. If multi-ferromagnetic materials are used, it is possible to achieve an ultra-high-rate reading and writing process at the same time." Said.
Broad prospects - storage density is hundreds of times higher than current technology
With the rapid development of wireless communication technology, information storage technology, electromagnetic interference technology, etc., people have put forward higher requirements for material selection and device miniaturization and integration design. The magnetoelectric heterostructure of single-molecule magnet has many advantages such as free conversion of energy between magnetic field and electric field and large magnetoelectric conversion coefficient. Therefore, it has broad application prospects in sensors, multi-state memories and RF microwave devices. In the interview, Wang Yuxia also revealed that they prefer to use chemical synthesis methods to try to introduce iron electrodeization by breaking the spatial inversion symmetry, enhance the magnetoelectric coupling effect, and realize the regulation of the electric field on the magnetic or magnetic field. Novel magnetoelectric materials that behave as molecular magnets and ferroelectrics.
“Single-molecule magnets show magnetic memory effects as a necessary factor for all data storage. In theory, using a single molecule for data storage can provide a hundred times higher data density than current technology.” Wang Yuxia said, this also means that single-molecule magnets have Broad application prospects.
At present, the magnetic structure of single-molecule magnets has been relatively clear. Wang Yuxia told reporters that the properties of single-molecule magnets can be predicted based on the configuration of the molecule. If the molecule belongs to a symmetrical configuration with large magnetic anisotropy, it is expected to become a single-molecule magnet. The reporter learned that in this experiment, Wang Yuxia and the research partners used the solution slow evaporation method to synthesize the rare earth lanthanum monomolecular magnet single crystal sample, the size of which reached the order of millimeters. In this crystal, the strong spin-orbit coupling erbium ions are in a slightly distorted octahedral coordination field, which has uniaxial anisotropy, which is favorable for the formation of single-molecule magnets. The low temperature magnetic relaxation behavior and magnetic anisotropy of the single molecule magnet were determined by measurement of AC susceptibility and DC magnetization. This research also laid a solid foundation for subsequent electrical continuous measurement observations.