Data Can Be Held in the Smallest of Things

The Hefty RAMAC 350

As technology progresses and our computing abilities grow, the need for more advanced data storage solutions arises. We’ve come a long way so far. Back in 1956, IBM released a revolutionary hard drive: the RAMAC 350, capable of storing a whole 5 Mb worth of data. It stored its data on 50 platters, each 24 inches in diameter, and the whole drive weighed about a ton. In modern day, the storage capabilities have increased dramatically as the size of drive required to house data continues to shrink. Recently, Nimbus Data released the ExaDrive DC100, a solid-state drive capable of holding 100 Tb of data which fits into a 3.5 inch form factor. The DC100 utilizes 3D NAND technology, meaning it takes the already existing NAND storage technology which arranges cells side-by-side for data storage, and stacks those layers of cells perfectly on top of one another to greatly expand the size of storage on the drive. In general, we are now capable of storing data on transistors 14 nm across, or about 14 times wider than a strand of our DNA. But as we move forward to increased data storage sizes, we approach a limit to how much data we can hold within a certain amount of space, and we must innovate new materials and solutions for data storage.

One avenue for this innovation may have been found recently by an international team of researchers led by Paul Ching-Wu Chu, founding director of the Texas Center for Superconductivity. The new technology utilizes what is known as a skyrmion: the smallest possible perturbation to a uniform magnet. A skyrmion is a point-like region surrounded by a field of spins. It can exist especially in lattice structures of solid materials. Its exact nature is complicated, but its applications to technology are very promising.

A vector field of 2D magnetic skyrmions

Skyrmions can be moved using very little electrical current, and present a possibility for a new type of data storage, wherein a bit is encoded based on the existence or non-existence of a skyrmion. However, there are some problems that come with skyrmions. Much like superconductors, another useful material composed of lattice-structure solids, skyrmions usually only exist at a very low and very small range of temperatures. For example, the material that Chu’s team has studied normally only exists in a skyrmion state at 55-58.5 K, a range of only 3.5 K. These temperatures would make it very difficult and cumbersome for the material to be used for data storage, but recent developments may have found a solution to this problem.

Room temperature skyrmions have been observed, and are not brand new (they have been observed as far back as 2015 when the idea for data storage using skyrmions was developed and studied). Chu’s team was able to achieve this using the compound copper oxyselenide, expanding the temperature range up to 300 K (just above to room temperature). It achieves this by putting the material under immense pressure. The skyrmion state was observed in Chu’s compound at 300 K when put under 8 GPa of pressure. However, this presents another problem similar to the original issue of temperature; 8 GPa is about 80,000 times more pressure than Earth’s atmosphere, meaning a storage material held at that pressure would need a large and expensive amount of specialty equipment. But none of this is breakthrough news yet. The exciting development from this team comes from the suggestion that for this material, atmospheric pressure can be substituted for chemical pressure to achieve stable room-temperature skyrmions.

Normal pressure the way we think of it is atmospheric pressure, the force of gas particles moving around and pushing against one another and the surfaces they come in contact with. This is an external pressure, pushing from the outside of the material (in this case, our lattice compound). Chemical pressure is achieved when adding chemical entities (atoms, ions, or molecules) into the lattice of a solid. This pressure can be changed with the size or charge of the inserted particles and has the unique ability to be either positive or negative, acting either with or against the external pressure. The act of inserting foreign particles into a lattice structure is commonly referred to as “doping” and has many applications.

The doping of a silicon system with boron

The suggested use of chemical pressure that comes from doping can be used as a substitute to atmospheric pressure, which could make a material capable of having room-temperature skyrmion states a commercially viable option for data storage. This is just one potential route among many for the future of high-density data storage, and shows us the interconnected nature of the development of chemistry and computational technology.