By Josh Perry, Editor
[email protected]

Researchers from Rutgers University (Newark, N.J.) and the U.S. Department of Energy (DOE) Brookhaven National Laboratory (Upton, N.Y.) have demonstrated a new X-Ray imaging technique that allowed scientists to visualize antiphase magnetic domains in antiferromagents (AFM).

Brookhaven Lab physicists Claudio Mazzoli (left) and Mark Dean at the Coherent Soft X-ray Scattering (CSX) beamline at the National Synchrotron Light Source II.
(Brookhaven National Lab)

These materials are an emerging topic in the field of spintronics, according to a report from Brookhaven, which is being considered as a future direction for next-generation electronics that are not as limited by the heat that they create.

“Conventional electronics such as computer chips rely on the transport of electrical charge carriers, or electrons, to operate. As these charges move around, they dissipate energy in the form of heat, limiting device efficiency,” the report explained. Spintronics exploits another intrinsic property of electrons: spin. Because electron spins can be flipped from one magnetic polarity to another much faster than charge can be moved around, devices based on spintronics can be intrinsically faster than today’s electronics.”

AFM are being considered for spintronics because the spin orientation can be flipped faster than conventional magnets and the magnetic fields or more controlled, which means that they won’t interfere with other sources of magnetization. The concern for scientists is how to control the spins of AFM and this is where the new imaging technique comes into play.

“The scientists directed a coherent beam of x-rays from the CSX beamline through a circular pinhole to illuminate the magnetic order of an iron-based AFM sample,” the report continued. “They set the beamline x-rays to an energy resonating with (close to) the energy of the spins in the material. A detector captured the intensity of the light as it reflected off the sample.”

The organization of the photons allowed the researchers to see the different antiphase domains and how they changed in real time, while being heated to remove the antiferromagnetic order and cooled to restore the order.

The research was recently published in Nature Communications. The abstract read:

“Manipulating magnetic domains is essential for many technological applications. Recent breakthroughs in Antiferromagnetic Spintronics brought up novel concepts for electronic device development. Imaging antiferromagnetic domains is of key importance to this field. Unfortunately, some of the basic domain types, such as antiphase domains, cannot be imaged by conventional techniques.

“Herein, we present a new domain projection imaging technique based on the localization of domain boundaries by resonant magnetic diffraction of coherent X rays. Contrast arises from reduction of the scattered intensity at the domain boundaries due to destructive interference effects.

“We demonstrate this approach by imaging antiphase domains in a collinear antiferromagnet Fe₂Mo₃O₈, and observe evidence of domain wall interaction with a structural defect.

“This technique does not involve any numerical algorithms. It is fast, sensitive, produces large-scale images in a single-exposure measurement, and is applicable to a variety of magnetic domain types.”