AIST Stories No1
7/36

Impact in the following fields! Community life◦Information technology◦Environment◦Electronics◦TelecommunicationsIndustryLeading the way AIST!5lost when the power supply is turned off. Therefore, the power must always be kept turned on while the memory is being used, so large amounts of electricity are required.Shinji Yuasa, Director of our Spintronics Research Center and a globally renowned leader in spintronics research, says: “As information processing is moved into the cloud, many people are storing their data over the Internet in data centers. As a result, the power consumption of data centers, which have large numbers of HDDs, is rapidly increasing. Data centers are said to account for 2% of all electricity consumption in developed countries. If we can reduce the power consumption of HDDs, we can achieve a very substantial energy saving.”Electronics makes use only of the electric charge of electrons, whereas spintronics uses not only the electric charge but also the magnetic nature of electrons, which is called “spin”. Spintronics, which could also be referred to as “future electronics”, has a broad range of applications, increasing the capacities and reducing the power consumption of HDDs, and also contributing to improvements in non-volatile memory. Low-power HDD magnetic heads*1 that take advantage of the effects of spintronics have already been commercialized and have achieved a global market share of 100%. That is, they are used in all of the HDDs being manufactured now!Non-volatile memory that retains data even when the power is turned off (such as magnetoresistive random access memory (MRAM)) has been developed but there is still much room for improvement in its capabilities. The development of a second generation of non-volatile memory with higher capabilities (including spin-transfer torque technology (STT-MRAM)) is now proceeding. Combining the technologies of magnetism with electronics What is spintronics?Research into two properties of an electron, electric charge and spin, has traditionally been divided between two fields: electronics, which is based on electric charge, and magnetics, which is based on spin.The achievements of electronics include transistors and large-scale integrated circuit (LSI) chips. Electronics is excellent for computing but has the disadvantage of volatility. From magnetics, magnetic recording technologies are used in HDDs. Magnetics is inappropriate for computing but has the advantage of enabling non-volatility. With the understanding that taking advantage of the two properties together would provide new devices suitable for fast computing and excellent in energy efficiency, the two fields were combined into spintronics, to develop new, high-performance devices.The most important aspect of spintronics is magnetoresistance effect*2. This is a phenomenon in which a current flowing in a ferromagnetic*3 material or a solid-state device is changed, meaning that the electric resistance is changed, by a change in magnetization or a magnetic field. The phenomenon was discovered long ago, in 1857, when Lord Kelvin discovered anisotropic magnetoresistance (AMR) effect.The history of magnetoresistance effect is effectively the history of spintronics. Here, the progress of the technology is reviewed.This discovery by Lord Kelvin in the 19th century was not put to use for about 130 years, because the changes in current and resistance caused by AMR (the MR ratio*4) were only 1–2% at room temperature. Because the changes were tiny, practical application was difficult.The next breakthrough was the discovery of giant at a glanceTerminologySpintronicsA field of research that uses both the electric charge and magnetism (spin) of the electrons in a solid. Typical devices utilizing spintronics include hard disc drive (HDD) magnetic heads and magnetoresistive random access memories (MRAM).n型材料Electric chargeElectron spinAn LSI chipAn HDDAn electronMagnetics・Magnetic recording ・Permanent magnets・TransformersSpintronicsA new field developing new-functionality devices that utilize both electric charge and spin.Large-capacity HDDs, magnetic sensors, non-volatile memories, ....Electronics・Diodes・Transistors・LasersMagnetoresistanceeffect*1 Magnetic head: A component, incorporated in a storage device such as an HDD, that magnetizes a material to write data and uses magnetic field changes to read data.*2 Magnetoresistance effect: A phenomenon in which electrical resistance changes in accordance with external magnetic fields.*3 Ferromagnetism: The property of being attracted by magnets. Materials with this property are said to be “ferromagnetic”. In large ferromagnetic bodies, there are often many different “magnetic domains”, regions within which north and south poles are aligned in the same direction. In an HDD, these magnetic domains are used for recording data.*4 MR ratio: A value representing the size of a magnetoresistance effect. The difference in resistance between two states of magnetization is divided by the resistance in one of the states. MR ratio is a performance index for various device applications.Impact in the following fields! Community life◦Information technology◦Environment◦Electronics◦TelecommunicationsIndustryLeading the way AIST!5lost when the power supply is turned off. Therefore, the power must always be kept turned on while the memory is being used, so large amounts of electricity are required.Shinji Yuasa, Director of our Spintronics Research Center and a globally renowned leader in spintronics research, says: “As information processing is moved into the cloud, many people are storing their data over the Internet in data centers. As a result, the power consumption of data centers, which have large numbers of HDDs, is rapidly increasing. Data centers are said to account for 2% of all electricity consumption in developed countries. If we can reduce the power consumption of HDDs, we can achieve a very substantial energy saving.”Electronics makes use only of the electric charge of electrons, whereas spintronics uses not only the electric charge but also the magnetic nature of electrons, which is called “spin”. Spintronics, which could also be referred to as “future electronics”, has a broad range of applications, increasing the capacities and reducing the power consumption of HDDs, and also contributing to improvements in non-volatile memory. Low-power HDD magnetic heads*1 that take advantage of the effects of spintronics have already been commercialized and have achieved a global market share of 100%. That is, they are used in all of the HDDs being manufactured now!Non-volatile memory that retains data even when the power is turned off (such as magnetoresistive random access memory (MRAM)) has been developed but there is still much room for improvement in its capabilities. The development of a second generation of non-volatile memory with higher capabilities (including spin-transfer torque technology (STT-MRAM)) is now proceeding. Combining the technologies of magnetism with electronics What is spintronics?Research into two properties of an electron, electric charge and spin, has traditionally been divided between two fields: electronics, which is based on electric charge, and magnetics, which is based on spin.The achievements of electronics include transistors and large-scale integrated circuit (LSI) chips. Electronics is excellent for computing but has the disadvantage of volatility. From magnetics, magnetic recording technologies are used in HDDs. Magnetics is inappropriate for computing but has the advantage of enabling non-volatility. With the understanding that taking advantage of the two properties together would provide new devices suitable for fast computing and excellent in energy efficiency, the two fields were combined into spintronics, to develop new, high-performance devices.The most important aspect of spintronics is magnetoresistance effect*2. This is a phenomenon in which a current flowing in a ferromagnetic*3 material or a solid-state device is changed, meaning that the electric resistance is changed, by a change in magnetization or a magnetic field. The phenomenon was discovered long ago, in 1857, when Lord Kelvin discovered anisotropic magnetoresistance (AMR) effect.The history of magnetoresistance effect is effectively the history of spintronics. Here, the progress of the technology is reviewed.This discovery by Lord Kelvin in the 19th century was not put to use for about 130 years, because the changes in current and resistance caused by AMR (the MR ratio*4) were only 1–2% at room temperature. Because the changes were tiny, practical application was difficult.The next breakthrough was the discovery of giant at a glanceTerminologySpintronicsA field of research that uses both the electric charge and magnetism (spin) of the electrons in a solid. Typical devices utilizing spintronics include hard disc drive (HDD) magnetic heads and magnetoresistive random access memories (MRAM).n型材料Electric chargeElectron spinAn LSI chipAn HDDAn electronMagnetics・Magnetic recording ・Permanent magnets・TransformersSpintronicsA new field developing new-functionality devices that utilize both electric charge and spin.Large-capacity HDDs, magnetic sensors, non-volatile memories, ....Electronics・Diodes・Transistors・LasersMagnetoresistanceeffect*1 Magnetic head: A component, incorporated in a storage device such as an HDD, that magnetizes a material to write data and uses magnetic field changes to read data.*2 Magnetoresistance effect: A phenomenon in which electrical resistance changes in accordance with external magnetic fields.*3 Ferromagnetism: The property of being attracted by magnets. Materials with this property are said to be “ferromagnetic”. In large ferromagnetic bodies, there are often many different “magnetic domains”, regions within which north and south poles are aligned in the same direction. In an HDD, these magnetic domains are used for recording data.*4 MR ratio: A value representing the size of a magnetoresistance effect. The difference in resistance between two states of magnetization is divided by the resistance in one of the states. MR ratio is a performance index for various device applications.

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