To increase the density of recorded information, one needs:

a) smaller memory sells carrying one bit of information

b) smaller reading heads

c) more sensitive reading heads: devices with
a very high resistance sensitivity to small values
of a magnetic field. This would convert a
weak magnetic field from left- or right-polarised
small ferromagnetic particles constituting magnetic
memory into electric signals processed in the electronic
circuit.

Physics of two effects leading to applications of ferromagnetic metals in design of magnetic readheads - Tunneling Magnetoresistance and Giant Magnetoresistance - are described on the webpage Lecture 12b.

Example of layered structures:
	Metallic contact Ferromagnet Normal metal Ferromagnet Metallic contact

Magnetisation	Magnetoresistance

Layered structures:
	Metallic contact Ferromagnet 1 thin insulator Ferromagnet -1 Normal metal Ferromagnet Metallic contact

4.11.2010