Scientists post a lower speed limit for magnetic recording

May 17, 2004
Magnetic recording

The speed of magnetic recording -- a crucial factor in a computer's power and multimedia capabilities -- depends on how fast one can switch a magnet's poles. An experiment at the Stanford Synchrotron Radiation Laboratory (SSRL) found that the ultimate speed of magnetic switching is at least 1,000 times slower than previously expected. The result, which appears in the April 22 issue of the journal Nature, has implications for future hard disk computer drive technologies.

In the push toward ever-faster magnetic recording, experts expected to find a physical limit, a threshold speed beyond which materials would respond chaotically. "If you had asked me a year ago, 'How fast does one have to create a pulse that does not switch magnetization?' my answer would have been one femtosecond (one thousandth of a trillionth of a second)," said Professor Joachim Stöhr, deputy director of SSRL. "Chaotic behavior was not expected in this experiment, which ran in the picosecond (trillionth-of-a-second) range."

In a computer hard drive, a writing head hovers over a disk that's rapidly spinning -- at up to 15,000 rotations per minute, or 150 times faster than a CD player. An electric current running in the head creates a magnetic field, which records data by turning tiny areas of the disk's surface into microscopic magnets. The disk is coated with a special, grainy material that allows only two, opposite directions of the magnetization, representing the 0 or 1 of a basic unit of data, or bit. High recording speed requires the coating material to respond and switch its poles quickly enough to record each bit reliably.

The challenge now will be to understand why the maximum speed seems to be at least 1,000 times lower than expected. The explanation, Siegmann said, could lie in the way thermal motion interacts with the magnetization process.

The limit on recording speed must be somewhere between 100 billion and a trillion bits per second, but is unlikely to ever affect technology, said Seagate's Weller. State-of-the-art drives can now record about 1 billion bits per second, and long before that speed can be increased 100-fold, other physical constraints will get in the way, he said. In particular, higher speed requires smaller magnetic grains, but their size cannot go below the size of atoms.

The SSRL result could be an important step toward understanding the basic physics of data recording, leading to the development of entirely new technologies. A promising idea, Weller said, is heat-assisted recording, where a small section of the recording medium is temporarily brought to a high temperature, to speed up its magnetization reversal.

Read more technical details about experiment on Stanford University News web-site.

Explore further: New insights found in black hole collisions

add to favorites email to friend print save as pdf

Related Stories

A new spin on Saturn's peculiar rotation

Mar 25, 2015

Tracking the rotation speed of solid planets, like the Earth and Mars, is a relatively simple task: Just measure the time it takes for a surface feature to roll into view again. But giant gas planets Jupiter ...

Protecting Earth from space weather

Mar 20, 2015

This week's spectacular glowing auroras in the night sky further south than usual highlighted the effect that 'space weather' can have on Earth.

What is Mars made of?

Feb 26, 2015

For thousands of years, human beings have stared up at the sky and wondered about the Red Planet. Easily seen from Earth with the naked eye, ancient astronomers have charted its course across the heavens ...

Recommended for you

New insights found in black hole collisions

Mar 27, 2015

New research provides revelations about the most energetic event in the universe—the merging of two spinning, orbiting black holes into a much larger black hole.

X-rays probe LHC for cause of short circuit

Mar 27, 2015

The LHC has now transitioned from powering tests to the machine checkout phase. This phase involves the full-scale tests of all systems in preparation for beam. Early last Saturday morning, during the ramp-down, ...

Swimming algae offer insights into living fluid dynamics

Mar 27, 2015

None of us would be alive if sperm cells didn't know how to swim, or if the cilia in our lungs couldn't prevent fluid buildup. But we know very little about the dynamics of so-called "living fluids," those ...

First glimpse inside a macroscopic quantum state

Mar 27, 2015

In a recent study published in Physical Review Letters, the research group led by ICREA Prof at ICFO Morgan Mitchell has detected, for the first time, entanglement among individual photon pairs in a beam ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.