How magnetic ID cards are becoming indestructable

A new magnetic memory technology that can't be erased through rough use is being developed.

cassette tape
Laurent Hoffman

One of the problems with traditional magnetic storage has always been that, because it's written with magnetic fields, it can be wiped by those fields too.

That makes for a pretty unstable medium—though convenient and more efficient than many.

Magnetic storage is used in ID and credit cards too, but the environments that the cards encounter are brutal on the media.

So is space travel, and indeed the residential living rooms with magnet-containing home theatre speakers, for example. Remember the mysteriously deteriorating cassette tape?

Yet magnetic media has its favorable qualities—it's more secure than Radio Frequency (RF) chips, for example.

Those chips can be eavesdropped on by passersby with equipment.

Magnetic permeability

A group of scientists think they might have come up with a solution to the damage issues. They say they have found a magnetic solution that's "not changed by exposure to magnetic fields," the Institute of Physics writes on its website.

It also isn't affected adversely by heat.

Magnetic permeability, as the technique is called, is a "property of 'soft' ferromagnets," the IOP says.

The scientists say in their findings that "there are no clear technological barriers to writing and reading permeability information cards." The paper is published in the Journal of Physics D: Applied Physics.

Importantly, the report points out that "information stored by programming changes in the magnetic permeability of each memory bit will not be erased by exposure to magnetic fields."


Now, lasers and microsecond-applications of heat are used to write the data onto layers of permalloy and copper. Ultimately, they are "radiation hard," the scientists say.

That's good for space travel, because weight could be reduced through reductions in radiation shielding.

The laser crystallizes "amorphous regions of ferromagnets," IOP says. "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."

That's more secure than RF chips because the probe needs to get closer to the media than an RF reader does to its vulnerable RF chip.

How much data?

"At present we have low density sized bits," Dr. Alan Edelstein, an author on the paper, said in the IOP article.

To make them nano-sized, more work needs to be done, they say.

For direct laser writing, which could be used for the ID cards, using "one micron wide bits, there would be 25 kilobits per inch in a magnetic strip," the paper says.

In other words, you won't be putting the works of Shakespeare on an indestructible magnetic card—for now.

No limits

The superparamagnetic limit, which is the size of the "particles used in the memory," restricts the amount of data that can be carried in magnetic storage.

Ultimately, that limit won't affect their new technology, the scientists say.

"We have the potential to get much higher since we are not limited by the superparamagnetic limit," Edelstein says.


"There is also the possibility of developing a type of RAM that will be a one-time programmable non-volatile magnetic memory," the scientists say in their paper.

And how do you re-write it? One of the advantages of traditional magnetic memory is that it's re-writable. The scientists say it's possible, and they're working to make it a reality.

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