3-D Imaging -- First Insights Into Magnetic Fields

Mar 30, 2008
Magnetic Fields Around a Dipol
The magnetic field of a dipol magnet visualized by spinpolarized neutrons. Credit: Hahn-Meitner-Institut Berlin

3-D images are not only useful in medicine; the observation of internal structures is also invaluable in many other fields of scientific investigation. Recently, researchers from the Hahn-Meitner-Institute (HMI) in Berlin in cooperation with University of Applied Sciences have succeeded, for the first time, in a direct, three-dimensional visualisation of magnetic fields inside solid, non-transparent materials. This is announced by Nikolay Kardjilov and colleagues in the current issue of the journal Nature Physics.

The researchers in the imaging group used neutrons, subatomic particles that have zero net charge, but do have a magnetic moment, making them ideal for investigating magnetic phenomena in magnetic materials. When in an external magnetic field, the neutrons behave like compass needles, all aligning to point on the direction of the field.

Neutrons also have an internal angular momentum, often referred to by physicists as spin, a property that causes the needle to rotate around the magnetic field, similar to the way in which the Earth rotates on its axis. When all of the magnetic moments point in the same direction then the neutrons are said to be spin-polarised. If a magnetic sample is irradiated with such neutrons, the magnetic moments of the neutrons will begin to rotate around the magnetic fields they encounter in the sample and the direction of their spin changes.

Kardjilov's group used this phenomenon as a measurement parameter for tomography experiments using two spin polarisers (which only allow the passage of neutrons whose spin points in a specific direction) to polarise and then analyse the neutrons. By detecting changes in the spins, it is possible to “see” the magnetic fields within the sample.

Kardjilov explains this by comparison with a medical CT scan; when a specimen is irradiated with x rays the density of the materials present alters the intensity of the light. "It's the same with our magnetic specimen, which changes the spin rotation of the neutrons", says Nikolay Kardjilov. "The equipment only allows passage of neutrons with a specific spin rotation, and this generates the contrast according to how the magnetic properties are distributed within the specimen. By rotating the specimen we can reconstruct a three-dimensional image."

Since 2005, Nikolay Kardjilov has built up the neutron tomography section at HMI and now his group is the first to use spin rotation as a measurement signal for three-dimensional imaging. Normally, neutron imaging relies on the different levels of absorption of radiation by different materials to produce contrast. The measurement of magnetic signals is a novel concept and its success lies partly in the polarisers and analysers, and the detector system, which have been developed and built by the HMI researchers.

Magnetism is one of the central research fields at HMI. To understand high temperature superconductivity, for example, it is vital to understand how magnetic flux lines are distributed and how these flux lines can be established in the material. With Kardjilov's experimental setup, it is now possible, among other things, to visualise magnetic domains in magnetic crystals three-dimensionally.

Source: Helmholtz Association of German Research Centres

Explore further: Sandia's Z machine receives funding aimed at fusion energy

Related Stories

Pulsar with widest orbit ever detected

May 01, 2015

A team of highly determined high school students discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT). ...

Intertwining of superconductivity and magnetism

Apr 28, 2015

Inelastic neutron scattering experiments on a copper-oxide superconductor reveal nearly static, spatially modulated magnetism. Because static magnetism and superconductivity do not like to coexist in the ...

Ultrafast tracking of electron spins

Apr 21, 2015

Our present digital information processing and storage is based on two properties of the electron. The first is its charge, which is used in electronic circuits to process information. The second is its spin, ...

Graphene looking promising for future spintronic devices

Apr 10, 2015

Researchers at Chalmers University of Technology have discovered that large area graphene is able to preserve electron spin over an extended period, and communicate it over greater distances than had previously ...

Penetrating the quantum nature of magnetism

Jun 17, 2013

Antiferromagnets are materials that lose their apparent magnetic properties when cooled down close to absolute zero temperature. Different to conventional magnets, which can be described with classical physics ...

Recommended for you

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

E_L_Earnhardt
5 / 5 (2) Mar 30, 2008
A wonderful addition to the study of living cells! Interaction of electron spins with neutron spins will help explain inteligence transfer, and energy routing!
earls
3 / 5 (2) Mar 30, 2008
That doesn't sound like very "neutral" behavior to me.
Ralph
4 / 5 (1) Mar 31, 2008
This little article is outstandingly well written. It is clear, concise and amazingly informative. Few general-audience science pieces meet this level of clarity and readability. I learned a lot about neutrons and about the new imaging technique by reading it. Kudos to the author!
HeRoze
4 / 5 (2) Mar 31, 2008
Cool- spin rotation technology is the fundamental response used in MRI imaging. MRI uses hydrogen spin alignments, but all else is similar. Good stuff.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.