3-D Magnet Map

For the first time, scientists have created a three-dimensional image of the magnetic field inside a solid, non-transparent material. The researchers, from the Hahn-Meitner-Institute (HMI) and the University of Applied Sciences in Berlin, detailed their results March 30 in the journal Nature Physics.

The scientists used neutrons to map the magnetic field. Since neutrons have no net electric charge, but do have a magnetic moment, they are useful for investigating magnetic phenomena. 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 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 Earth rotates on its axis. When all of the magnetic moments point in the same direction, the neutrons are said to be spin-polarised.

If a magnetic sample is irradiated with 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. The researchers were able to map the magnetic fields within the sample by detecting changes in the neutrons' spins.

Image Credit: Hahn-Meitner-Institut Berlin

• Video: Generating a Giant Magnet
• When North Becomes South: New Clues to Earth's Magnetic Flip-Flops
• Discovery Changes Understanding of Neutrons