Combining chips and drives

in today's information world, bits of data are processed by semiconductor chips, but stored in magnetic disc drives. Limitations of this technology have made the world of electronics anxiously wait for a device that can transmit as well as store information. Now, researchers at the Sweden-based Royal Institute of Technology (kth) have made a 'spintronic ferromagnetic material', which displays both magnetic and semi-conducting properties, and functions at room temperature. The material would be ideal to make the device that transmits and stores data. "The next generation electronics may no longer be a distant dream," says K V Rao of the department of material sciences at kth, who headed the research. The work was mainly done by researchers of Indian origin.

With every passing day, electronic chips have become tinier, but the number of transistors packed on them has increased. The total length of all the wires that connect the transistors on a Pentium chip at present is more than 1.5 kilometres! Moore's Law -- a dictum religiously followed by the electronics industry -- states that the number of transistors that fit on a computer chip would double every 18 months. However, sooner or later it would not be possible to cram more transistors onto a chip due to some fundamental roadblocks -- as the number of transistors increases, the devices are plagued by a big problem: energy loss (which is inevitable as signals pass from one transistor to another). The more the transistors, the greater would be the energy loss. There is another hitch: with the chip becoming smaller than 100 nanometres (one-billionth of a metre), electrons (the basic building block of electronics used for transmitting information in transistors) will behave more like waves than particles. This may affect the communication process. Scientists are not certain how the wave-like behaviour will influence the performance of the gadgets.

Due to these hurdles, developing the 'optimum chip' seemed a Herculean task for long. However, scientists came up with a way out -- a single substance that could store as well as transmit information. To make this possible, they tried making a new class of ferromagnetic materials, which are known to have magnetic and semi-conducting properties. In theory, the new ferromagnetic material could also help prevent energy loss by exploiting the non-uniform orientation of the electrons. If the orientation could be made uniform (with the help of an electrical charge), then it would be possible to develop multifunctional 'spin-based' electronic devices that would be ultra-fast and efficient. Ferromagnetic substances can be made 'spintronic' by doping semi-conducting materials such as zinc oxide (zno) with magnetic impure elements like manganese (mn).

However, in the laboratories, the dreams of the scientists could not come true. The ferromagnetic property of mn-doped zn o or mn-doped gallium nitride (gan) could not be retained as very high temperature (more than 700c) was used to make them. A few endeavours that succeeded could produce substances that functioned much below room temperature -- a range unfeasible for practical purposes.

kth researchers have made spintronic ferromagnetic material which operates above room temperature. They used a low-temperature process to achieve the feat. After mixing zno and manganese oxide, they calcinated the mixture at 400c for eight hours. Thereafter, it was sintered (converting a substance from powder to solid form at very high pressure and temperature) in the range 500-900c to obtain ceramic pellets. The pellets sintered at temperatures less than 700c retained their ferromagnetic character; but those prepared at temperatures above 700c were anti-ferromagnetic due to the clustering of mn atoms. The clustering happened as the mn atoms replaced zn atoms in a non-homogeneous manner. "This affects the magnetic properties," explains Rao.

The scientists have also prepared ferromagnetic thin films of mn-doped zno. Ferromagnetic powder of mn-doped zno can also be made. "The feat opens up the possibility to fabricate a wide range of components for spintronics," the scientists claim. They have applied for patent, and have also formed a company to market the technology.

Subscribe to Daily Newsletter :

SUPPORT US

We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.