Researchers all over the globe have been working hard on new memory storage devices that are faster, more stable, and can be made smaller than flash memory, which is approaching its fundamental limit on size, largely set by semiconductor physics. An international team of researchers has provided the first evidence that this size barrier can be broken. They found that the boundaries between magnetic regions in an electrical insulator can become electrically conductive, a controversial phenomenon postulated decades ago but never experimentally observed until now.
By sending microwaves to a metal tip ~100 nanometers in diameter and sensing the reflected waves (microwave impedance microscopy, or MIM), they receive images that reveal whether a material is insulating or conductive in a small region similar to the tip in size. These results were correlated with measurements at ALS Beamline 12.3.2, where the Laue x-ray microdiffraction instrument gave insights into the crystal orientation of the investigated material leading to important conclusions on the nature of the conductive curves observed by MIM.
In the end, anything that can be switched between two states can store information. If the state is stable, it’s called “nonvolatile.” For electronic nonvolatile memory that works within a circuit, these two states are often associated with whether a device can conduct electricity or not. The studied material can realize this property in a novel way: it is insulating by itself, but turns conductive when conductive magnetic boundaries are formed inside. Memory devices based on this new phenomenon can potentially go beyond the size limit of flash.
Work performed at SLAC National Laboratory, RIKEN (Japan), Shanghai Institute of Microsystem and Information Technology (China), and ALS Beamline 12.3.2.
Eric Yue Ma, Yong-Tao Cui, Kentaro Ueda, Shujie Tang, Kai Chen, Nobumichi Tamura, Phillip M. Wu, Jun Fujioka, Yoshinori Tokura, and Zhi-Xun Shen, “Mobile metallic domain walls in an all-in-all-out magnetic insulator,” Science 350, 538 (2015).