1. Magnetic recording technology
Krupa Maria Kuruvila

2. Nanomagnets
A nanomagnet is a submicrometric system that presents spontaneous magnetic
order at zero applied magnetic field (remanence).
The small size of nanomagnets prevents the formation of magnetic domains.

3. Why nanomagnetism?

4. PARTS OF A MODERN HARD DRIVE
High speed spinning discs-made of microscopic magnetised metal grains.
Recording head flying over each surface-to write the data-electromagnet
Reading head- to read the data.

5. HARD DRIVE
The motor of the disc and the motor of the actuator arm
work collaboratively to align a desired bit over the read
head or the write head to a given time to read or write.
Magnetic logic systems can be very fast.
It can retain the information even when the power
is switched off.

6. MAGNETIC RECORDING TECHNOLOGY
Magnetic memory or magnetic data storage is a key
component in computer operation.
Principle: the ability of magnets to magnetize other materials
and the ability of those materials to attain the magnetization
and forced to change again by another magnetic field.
An object can be magnetised with north or south pole
in either end. N S S N
Ferromagnet-high susceptibility to magnetization.
The strength of which depends on that of the applied magnetizing field, and which may persist after removal of the applied field. 

7. Representing 1’s and 0’s magnetically
Data are stored in a computer in series of ones and zeroes(1’s and 0’s)-Binary code.
A bit is the smallest unit of data storage.
It can be visualised as a mini scale block that can be magnetised into a permanent magnet.
Microscopic magnetised metal grains

8. Every red and blue block in this
picture is a bit.
Red blocks have north poles facing up and the blue blocks have north poles facing down.
The computer recognises this as ones and zeroes.
Grey blocks are the empty bits that are not yet magnetised.
The write head is basically an electromagnet.
To direct the magnetic field into the bit to magnetize it as it passes by.

9. It magnetise the material with a north facing up and a south facing down, by changing the direction of the current.
Reversing the direction of current results in the reversing of current in the magnetic field.
Once written the data can be read by the read head by recognising the direction of the magnetic field as it goes over a written bit.