Advanced Light Source (ALS) studies helped scientists understand how a nanoscale magnetic lattice (an artifical spin ice) acts as a toggle switch for x-ray beams with spiral character.
SIGNIFICANCE AND IMPACT
The findings represent an important step toward the development of a versatile new tool for probing or controlling exotic phenomena in electronic and magnetic systems.
A curious singularity
Artificial spin ices (ASIs) are engineered arrays of nanomagnets that are often “frustrated,” meaning that the magnets, constrained by geometry, cannot align themselves to minimize their interaction energy. Water ice exhibits a similar property with regard to the positioning of hydrogen atoms.
While studying ASIs, a collaboration between scientists from the University of Kentucky and the ALS (see related feature article) made an interesting observation: light scattered from certain ASIs produced diffraction patterns in which spots of constructive interference were shaped like donuts instead of dots. The donuts were indicative of a phase singularity—a hallmark of light with a property known as orbital angular momentum (OAM).
Read more on the ALS website
Image: When x-rays are scattered from a patterned array of nanoscale magnets with a lattice defect, the beams acquire a spiral character (orbital angular momentum, or OAM) that produces diffraction patterns with donut-shaped spots. Researchers have found that these OAM beams can be switched on and off by adjusting the temperature or applying an external magnetic field.