Nav: Home

Physics for the mechanism of slow change in microscopic magnetic structures revealed

December 16, 2015

The research group of Professor Hideo Ohno and Associate Professor Shunsuke Fukami of Tohoku University has studied in detail, a slow change of microscopic magnetic structures in metallic wires induced by external driving forces, commonly called "creep" motion. This has allowed them to clarify the physics of how the driving forces, magnetic fields or electric currents, act on the magnetic structure.

Previous studies had shown that while the actions of magnetic fields and currents are the same for metallic materials, they are fundamentally different for semiconductor materials.

The present study reveals that in cases where the sample satisfies a certain condition, the current acts on the magnetic structure in a different manner from the magnetic field case, irrespective of the intricacies of the material.

The development of a high-performance magnetic memory device (where the magnetic structure is manipulated by current) has been intensively pursued recently, and the present findings are expected to facilitate the fundamental understanding to achieve the practical application.

The research group fabricated a wire device consisting of a ferromagnetic metal CoFeB, and investigated the universality class of a magnetic domain wall "creep". They evaluated the domain wall velocity for various magnitudes of magnetic field or electric current while keeping the device temperature constant, from which they derived the scaling exponent for the universality class.

The results indicate that the scaling exponent does not depend on factors such as temperature and wire width, for both magnetic field and current cases, confirming the universality of the observed feature. Interestingly, unlike the previous study on metallic systems, they found different universality classes between magnetic field and current-driven domain wall creeps in the present metallic sample.

This means that the actions of a magnetic field and current on the domain wall are fundamentally different from each other. The field-driven "creep" was found to belong to a previously known universality class, whereas the current-driven "creep" was found to belong to a different universality class which cannot be explained by the present theories and the scaling exponent was similar to the one observed previously in the magnetic semiconductor.

From detailed investigations of the behavior of the domain wall under the application of a current, they found that the current gives rise to an adiabatic spin-transfer torque acting on the domain wall which has a different symmetry to the torque induced by a magnetic field. In other words, it was clarified that, for sample in which stack structure is designed so that the adiabatic spin-transfer torque dominantly affects the domain wall, universal creep characteristics appear irrespective of the nature of material, such as metal or semiconductor, the details of microscopic structure.

The obtained findings shed light on a statistical physics of creep motion of elastic interfaces and development of high-performance magnetic memory devices.
-end-


Tohoku University

Related Magnetic Field Articles:

Understanding stars: How tornado-shaped flow in a dynamo strengthens the magnetic field
A new simulation based on the von-Kármán-Sodium (VKS) dynamo experiment takes a closer look at how the liquid vortex created by the device generates a magnetic field.
'Quartz' crystals at the Earth's core power its magnetic field
Scientists at the Earth-Life Science Institute at the Tokyo Institute of Technology report in Nature (Fen.
Brightest neutron star yet has a multipolar magnetic field
Scientists have identified a neutron star that is consuming material so fast it emits more x-rays than any other.
Confirmation of Wendelstein 7-X magnetic field
Physicist Sam Lazerson of the US Department of Energy's Princeton Plasma Physics Laboratory has teamed with German scientists to confirm that the Wendelstein 7-X fusion energy device called a stellarator in Greifswald, Germany, produces high-quality magnetic fields that are consistent with their complex design.
High-precision magnetic field sensing
Scientists have developed a highly sensitive sensor to detect tiny changes in strong magnetic fields.
Brilliant burst in space reveals universe's magnetic field
Scientists have detected the brightest fast burst of radio waves in space to date -- locating the source of the event with more precision than previous efforts.
Optical magnetic field sensor can detect signals from the nervous system
The human body is controlled by electrical impulses in the brain, the heart and nervous system.
What did Earth's ancient magnetic field look like?
New work from Carnegie's Peter Driscoll suggests Earth's ancient magnetic field was significantly different than the present day field, originating from several poles rather than the familiar two.
Just what sustains Earth's magnetic field anyway?
Earth's magnetic field shields us from deadly cosmic radiation, and without it, life as we know it could not exist here.
Ironing out the mystery of Earth's magnetic field
The Earth's magnetic field has been existing for at least 3.4 billion years thanks to the low heat conduction capability of iron in the planet's core.

Related Magnetic Field Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...