Magnetic permeability - an intrinsic property of 'soft' ferromagnets - is not changed by exposure to a magnetic field, unlike conventional magnetic memory, and therefore information stored by programming changes in the magnetic permeability of each memory bit will not be erased by exposure to magnetic fields.
"It was a big step just coming up with the idea of using magnetic permeability to store information, and coming up with a practical way of getting the memory near the sensor so that it can be read" explained Dr Alan Edelstein, an author on the paper. "I was surprised and pleased that we could make this approach work."
The technique used thermal heating with a laser to crystallise amorphous regions of ferromagnets. As the crystalline areas have a lower permeability than the amorphous areas, information can be read from the memory by reading the changes in a probe magnetic field.
With credit cards, RF chips have offered a more stable form of memory, but these can be read by a passer-by using an RF reader. As the probe magnetic field needs to be in close vicinity to the memory, this technique offers a more secure technology.
The researchers are now working on a technique to make the memory re-writable. "We've demonstrated the ability to rewrite bits for a read/write memory, and hope to publish the results soon." concluded Edelstein.
