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23.04.2013

Packing in magnetic recording by laser heating

Until recently, record density in this configuration was limited by the size of the focal spot of the laser. Scientists from Seagate Technology proposed the use the optical nanoantenna for the concentration of electromagnetic radiation. Data density on magnetic disks doubled every three years since their invention in 1955. Today the record density is approximately 500 GB per square inch. In the late '90s, with the invention of vertical magnetic recording disk capacity grew very quickly. However, the limit for record density increase will be reached soon related to the smallest possible size of a magnetic domain. When a certain critical size is reached magnetic domains of cobalt alloy become unstable and can switch spontaneously. The slightest heat will inevitably lead to data loss. There are materials called hard ferromagnetic materials that have much smaller minimum stable domain size. However, to change the polarity of the domain is only possible at elevated temperatures. When using HAMR, the minimum possible area of ​​heating is determined by the minimum size of the focused laser spot, i.e. 200 nanometers (diffraction limit for blue light).

 

To overcome the diffraction limit that restricts the minimum heating area scientists from Seagate suggested the use of plasmons, i.e. bound states of light wave and electron oscillations in metal. The light is focused on a 200 nanometer gold plate with 15-nanometer sharp. The interaction of electromagnetic wave and metal generates surface plasmons, i.e. energy waves which oscillate along the surface and create the intense electric field at the edge. Plasmon transducer serves as an antenna for concentration the light electromagnetic wave on the area smaller than the diffraction limit. Information recording on the pre-heated by laser area is made magnetically.

Such a method of local heating will possibly increase the density of magnetic recording up to 50 terabytes per square inch.

 

Source: Laser-Portal


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