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Researchers surprisingly discover quantum power in the hard disk material

Scientists at Argonne have discovered a way to control the direction of electron rotation in a cobalt iron alloy that affects its magnetic properties. The result can have consequences for more powerful and energy-efficient materials for information storage. Credit: Argonne National Laboratory Researchers find surprising ways to influence information storage properties in metal alloy. Sometimes scientific discoveries can be found along narrow roads. It turned out that a cobalt iron alloy material usually found on hard drives. As reported in a recently published version of Physical Review Letters researchers from the US Department of Energy (DOE) Argonne National Laboratory, along with Oakland University in Michigan and Fudan University in China, have found a surprising quantum effect in this alloy. The effect means the ability to control the direction of the electron direction, and it can allow researchers to develop more powerful and energy-efficient materials for information storage. By changing the direction of rotation of the electron in a material, the researchers could change their magnetic state. This greater control of magnetization enables more information to be stored and retrieved in a smaller space. Greater control can also provide additional applications, such as more energy efficient electric motors, generators and magnetic bearings. The effect the researchers discovered has to do with "damping", where the direction of the electron direction controls how the material is dispersed energy. "When you drive your car down on a flat highway with no wind, the release energy from the drag is the same no matter what…

Scientists at Argonne have discovered a way to control the direction of electron rotation in a cobalt iron alloy that affects its magnetic properties. The result can have consequences for more powerful and energy-efficient materials for information storage. Credit: Argonne National Laboratory

Researchers find surprising ways to influence information storage properties in metal alloy.

Sometimes scientific discoveries can be found along narrow roads. It turned out that a cobalt iron alloy material usually found on hard drives.

As reported in a recently published version of Physical Review Letters researchers from the US Department of Energy (DOE) Argonne National Laboratory, along with Oakland University in Michigan and Fudan University in China, have found a surprising quantum effect in this alloy.

The effect means the ability to control the direction of the electron direction, and it can allow researchers to develop more powerful and energy-efficient materials for information storage. By changing the direction of rotation of the electron in a material, the researchers could change their magnetic state. This greater control of magnetization enables more information to be stored and retrieved in a smaller space. Greater control can also provide additional applications, such as more energy efficient electric motors, generators and magnetic bearings.

The effect the researchers discovered has to do with “damping”, where the direction of the electron direction controls how the material is dispersed energy. “When you drive your car down on a flat highway with no wind, the release energy from the drag is the same no matter what direction you travel,” says Argonne material researcher Olle Heinonen, a study author. “With the effect we discovered it is as if your car is experiencing more moves if you travel north-south than if you are traveling east-west.”

“Technically, we discovered a significant effect of magnetic attenuation in nanoscale layers of cobalt-iron alloy coated on one side of a magnesium oxide substrate,” added Argonne material researcher Axel Hoffmann, another study author. “By controlling the electron spin, the magnetic attenuation dictates the frequency of energy dissipation, controlling aspects of the magnetization.”

The team’s discovery proved particularly surprising since the cobalt iron alloy had been widely used in applications such as magnetic hard disks for many decades, and its properties have been thoroughly investigated. It was conventional wisdom that this material did not have a preferred direction for electron rotation and thereby magnetization. In the past, the researchers prepared the alloy for use by “baking” it at high temperature, ordering the arrangement of cobalt and iron atoms in a conventional grid, eliminating the directional effect. The team observed the effect by examining untreated cobalt iron alloys in which cobalt and iron atoms can randomly occupy each other’s websites.

The team could also explain the underlying physics. In a crystal structure, atoms normally sit at regular intervals in a symmetrical arrangement. In the crystal structure of some alloys, there are small differences in separation between atoms which can be removed by the baking process; These differences remain in an “unoccupied” material.

Shrinkage of such material at the atomic level also changes the separation of the atoms, resulting in different interactions between atomic distortions in the crystalline environment. This difference explains how the attenuation effect on the magnetization is large in some directions and small in others.

The result is that very small distortions in the atomic arrangement of the crystalline structure of cobalt-iron alloy have giant implications for the damping effect. The team ran calculations at the Argonne Leadership Computing Facility, a DOE Office of Science User Facility, which confirmed their experimental observations. The work of the researchers is shown in the March 21

online edition of Physical Review Letters and has the title “Giant Anisotropy of Gilbert Suppression in CoFe Epitaxial Films”.


Harddrive boost comes in stock of iron and cobalt


More information:
Yi Li et al., Giant Anisotropy or Gilbert Damping In Epitaxial CoFe Films, Physical Review Letters (2019). DOI: 10,1103 / PhysRevLett.122.117203

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Argonne National Laboratory

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Spider doctor: Researchers discover surprising quantum effect in the hard disk (2019, April 25)
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