Proposed a principle of nanomagnetism, in which the spin direction changes on its own upon applying electric current without external spins. Expected to accelerate commercialization based on a paradigm shift from conventional spin memory devices
Credit: Korea Institute of Science and Technology(KIST)
The Korea Institute of Science and Technology (KIST) has announced that the research team led by Dr. Kim Kyoung-Whan at the Center for Spintronics has proposed a new principle about spin memory devices, which are next-generation memory devices. This breakthrough presents new applicability that is different from the existing paradigm.
Conventional memory devices are classified into volatile memories, such as RAM, that can read and write data quickly, and non-volatile memories, such as hard-disk, on which data are maintained even when the power is off. In recent years, related academic and industrial fields have been combining their advantages to accelerate the development of next-generation memory that is fast and capable of maintaining data even when the power is off.
A spin memory device is a device that stores data of 0 and 1 in the N pole and S pole directions, respectively, of a very small nanomagnet. It is widely applied in hard disks because the directions of the N pole and S pole are maintained even when the power is off. Thus, the successful commercialization of next-generation spin memory depends on how quickly and easily it can be controlled in the N pole and S pole directions of a nanomagnet.
Until now, spin was injected from the outside to control the N pole and S pole directions of a nanomagnet. Here, spin is a basic unit of magnetism that cannot be divided further, and numerous spins with the same directions as the N pole and S pole are gathered to form a single magnet. Therefore, if many spins are injected into a nanomagnet from the outside, the N pole and S pole directions of the nanomagnet can be controlled. However, its commercialization is arduous because generating and injecting external spins is not energy-efficient.
Recently, it has been reported that spins are formed inside a nanomagnet if electric current is applied to the nanomagnet. However, because no theory on how to analyze the behavior of such spins has been established yet, there has been no studies on the physical results of these spins.
Dr. Kim Kyoung-Whan at the KIST has established a theoretical system by developing a spin diffusion equation that describes the spin conductance in magnetic materials. It was discovered that when the spins formed by electric current is emitted to the outside, only the sign is opposite to that of the spins injected from the outside, and the effects are the same. Therefore, the directions of the N pole and S pole can be controlled by the nanomagnet itself without external spin injection, and the power consumption can be reduced by up to ~60% compared to that of conventional spin devices. Furthermore, memories can be developed in simple structures because they do not need the conventional structure for injecting external spins.
Dr. Kim Kyoung-Whan said, “This study provided an academic basis for spin conductance in magnetic materials. Furthermore, through the new paradigm, it is expected to contribute significantly to solving the optimization problems of power consumption, production yield, etc., which have been the biggest obstacles to the implementation of next-generation spin devices.”
This study was supported by the Ministry of Science and ICT (MSIT), as part of the Institutional R&D Program of KIST, and the New Research Support Program of the National Research Foundation of Korea. The research results were published in the latest issue of Physical Review Letters(Impact factor: 8.385), a journal in physics.
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