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 study refines biological evolution model

add to favorites email to friend print save as pdf

Related Stories

Cambridge team breaks superconductor world record

Jun 26, 2014

A world record that has stood for more than a decade has been broken by a team led by University of Cambridge engineers, harnessing the equivalent of three tonnes of force inside a golf ball-sized sample ...

Taking pictures with protons

Jun 18, 2014

A new facility for using protons to take microscopic images has been commissioned at the ring accelerator of the GSI Helmholtzzentrum für Schwerionenforschung GmbH (Helmholtz Centre for Heavy Ion Research) ...

Discovering a hidden source of solar surges

Jun 03, 2014

Cutting-edge observations with the 1.6-meter telescope at Big Bear Solar Observatory (BBSO) in California have taken research into the structure and activity of the Sun to new levels of understanding. Operated ...

Solving sunspot mysteries

Jun 03, 2014

Multi-wavelength observations of sunspots with the 1.6-meter New Solar Telescope at Big Bear Solar Observatory (BBSO) in California and aboard NASA's IRIS spacecraft have produced new and intriguing images ...

Recommended for you

New study refines biological evolution model

21 hours ago

Models for the evolution of life are now being developed to try and clarify the long term dynamics of an evolving system of species. Specifically, a recent model proposed by Petri Kärenlampi from the University ...

Production phase for LSST camera sensors nears

23 hours ago

(Phys.org) —A single sensor for the world's largest digital camera detected light making its way through wind, air turbulence, and Earth's atmosphere, successfully converting the light into a glimpse of ...

User comments : 0