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474 || AWSAR Awarded Popular Science Stories - 2019
states, either magnetized “1” or demagnetized “0,” with the help of an external stimulus, which is electricity in the present case.
With the ever-increasing demand for data storage, an alternate storage mechanism of
Chart 1. Units of digital signal storage capacity.
higher efficiency is highly anticipated. One drawback of the current material is that the magnetic domain, which saves one digit of information, consists of several millions of atoms. So, a large number of atoms/digits are used here.
In our laboratory at IISER,
Bhopal, we are trying to address
this problem by reducing
these million atoms to one
atom system. Means, we are
aiming to design one molecule
that will be able to show two
different magnetic states using
an external stimulus. Till now,
electricity has been used as
an external stimulus, but now
researchers are focusing on
light as a stimulus because of
its cost-effectiveness and eco-
friendly nature. Means, if we are
able to design such a molecule,
deposit it on the metal surface,
and use it as the magnetic coating on a hard drive and then as a light source, we can read and write on the hard drive. When we want to read or write the data, we can use a particular laser light that will magnetize certain molecules
and the data will be stored. Therefore, the presence of laser light will then be counted as “1,” and its absence will be counted as “0” (Scheme 1). To remove the data, another wavelength of laser light can be used, which will demagnetize the magnetized region. When we can use one molecule as a digit instead of millions of molecules as a digit, it will bring about a revolution in data storage science.
To achieve this target, we have to consider two aspects. First, the molecule should have a permanent magnetic moment, and second, the magnetic moment should be sensitive to external stimuli (preferably light) so that the information can be controlled by some external stimuli. One molecule can have a permanent magnetic dipole if it has unpaired electrons in it. Iron (Fe) is an abundant element on earth, which has unpaired electrons and shows a unique magnetic bi-stable property called spin crossover (SCO). SCO active molecules
change their spin states (number of unpaired electrons) on exposure to external stimuli such as heat, light, and pressure. This change in the spin state leads to a magnetic response, which can be used to read/write the data. We are synthesizing several molecules with iron (Fe) showing SCO behavior, where we can control the magnetic moment of the molecules with the help of external stimuli.
One such molecule is being explored by our group (Inorg. Chem. 2019, 58, 1134−1146). In this molecule,
we have considered both magnetic and optical aspects. The molecule contains Fe (III) having five unpaired electrons and it shows SCO behavior. For the optical purpose, we have used an azo-benzene-based molecule that
If we consider a computer as a living being, then the electricity is the blood and the hardware are the organs. The hard drive is the part of the brain (hardware) where memory (data) is stored. The hard drive is coated with a magnetic material that can be magnetized or demagnetized using electricity.