Two University at Buffalo materials researchers have developed an extremely sensitive nanoscale device that could shrink ultra-high-density storage devices to record sizes.
According to UB researchers Harsh Deep Chopra and Susan Hua, the magnetic sensor, made of nickel and measuring only a few atoms in diameter, could increase data storage capacity by a factor of a 1,000 or more and could lead to supercomputing devices as small as a wristwatch.
As stored ‘bits’ of data get smaller, their magnetic field gets weaker, making the bits harder to detect and read. Reliable reading of the data depends on producing a large enough magnetically induced change in the electrical resistance of the sensor. Producing a detectable change at room temperature is another challenge.
In an experiment at UB, Chopra and Hua demonstrated that their tiny sensor produces an unusually large change in resistance in an ultra-small magnetic field at room temperature. The magnitude of the magnetic effect they created is said to surpass all previous records.
The effect is based on spintronics, a rapidly growing field that employs not only the charge, but also the spin of electrons in making electrical devices.
The current technology used in the heads, or sensors, that read bits from a storage disk, is based on an effect called giant magnetoresistance (GMR). GMR refers to the change in the sensor resistance when placed in a magnetic field. The effect is typically less than 100 percent.
Inside a hard drive, a GMR device senses the local magnetic field of a stored bit of data. Such sensors have enabled commercial hard drives that can store the amount of data contained in a DVD full-length movie in a space the size of a credit card.
The effect created with the new nickel device is called ballistic magnetoresistance (BMR) and employs an electrical conductor that is only a few atoms wide and long.
The BMR experiment exhibited a record change in sensor resistance of more than 3,000 percent. Chopra predicts the ultimate capacity will be about a terabit per square inch. This could enable the storage of 50 or more DVDs on a hard drive the size of a credit card.
Besides being useful for the multi-billion-dollar data-storage industry, the BMR techniques could improve magnetic measurements and the study of magnetic effects in individual atoms, molecules and nanoscale clusters.
It could also greatly enhance resolution and sensitivity of scanning probe-imaging techniques that are widely used to characterise magnetic materials.