Manufacturing Bits: April 5

Open access superconducting magnets; magnetic nanodevices.


Open access superconducting magnets
The National High Magnetic Field Laboratory or MagLab has opened the world’s strongest superconducting magnet to users.

In the works for eight years, the 32 tesla (T) all-superconducting magnet enables scientists to conduct research for various applications, such as quantum matter experiments. The system is called the SCM-32 T.

MagLab develops several different types of large and powerful magnets. Dozens of measurement techniques can be performed at the MagLab’s user facilities. There is no cost to scientists to use MagLab’s magnets. Researchers can submit a proposal here.

Tesla, or T, is the measurement of magnetic field strength. A refrigerator magnet has a field of 0.01 T. An MRI scanner has a 1.5 tesla magnet. A 32 T magnet is more than 3,000 times stronger than a refrigerator magnet, according to MagLab.

Superconducting magnets are based on superconductors, which conduct electricity without resistance. The 32 T magnet is built using low-temperature superconductors called YBCO. They are composed of yttrium, barium, copper and oxygen.

The system combines a 15 T low-temperature superconducting outsert and a 17 T high-temperature superconducting insert. The magnet system operates in a bath of liquid helium at 4.2 Kelvin (K). The SCM-32 T is housed in a lab with a specially-designed millikelvin research space. Experiments are conducted down to temperatures within 14 thousandths of a K above absolute zero.

The first users measured nuclear magnetic resonance of a magnetic system with a spin nematic state. “Researchers will now have an opportunity to leverage this instrument to make important research discoveries that will expand our understanding of the physics of complex quantum materials,” said Tim Murphy, DC field facility director at MagLab.

Magnetic nanodevices
Riken and others have taken a major step towards the development of a technology called magnetic nanodevices.

The development of these devices require the electrical generation of rotation or torque. This is practical with many of today’s systems. For example, the ability to use electric currents to rotate mechanical parts enabled the development of electric motors and other products.

For some time, researchers are trying to do the same thing with magnetic nanodevices at the nanoscale. But there are some challenges to enable efficient torque.

“Usually, torque is generated in magnetic systems by converting electric charge to spin by using the strong spin–orbit interaction of a heavy-metal layer,” according to researchers from Riken. “The resulting spin current is then injected into adjacent ferromagnetic layers. But heavy-element materials are often incompatible with scalable production processes, and their high resistance makes them unsuitable for some applications.”

In response, Riken and others have devised an efficient torque generation for magnetic nanodevices. This has been accomplished in an three-layer system based on a ferromagnetic layer, a copper layer and an alumina (Al2O3) layer. In theory, the orbital angular momentum is generated at the copper–alumina interface. The energy is transported by the copper layer to the ferromagnetic layer. It is converted into spin.

“Despite the absence of heavy elements, their effective spin Hall conductivity can be one order of magnitude larger than those of heavy-metal based multilayers. Properties of the measured torque deviate from those of the spin-injection induced torque and are consistent instead with a recently proposed torque mechanism based on orbital angular momentum injection. Our results demonstrate a direction for magnetic nanodevices based on the orbital angular momentum injection,” said Junyeon Kim from Riken in Physical Review, a technology journal.

Pohang University of Science and Technology, Forschungszentrum Jülich, Johannes Gutenberg University, The University of Tokyo, and the Asia Pacific Center for Theoretical Physics contributed to the work.

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