Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Changing the rings: a key finding for magnetics design

07.08.2007
Researchers at the National Institute of Standards and Technology’s Center for Nanoscale Science and Technology (CNST) have done the first theoretical determination of the dominant damping mechanism that settles down excited magnetic states—“ringing” in physics parlance—in some key metals.

Their results, published in the Physical Review Letters,* point to more efficient methods to predict the dynamics of magnetic materials and to improve the design of key materials for magnetic devices.

The ability to control the dynamics of magnetic materials is critical to high-performance electronic devices such as magnetic field sensors and magnetic recording media. In a computer’s magnetic storage—like a hard disk—a logical bit is represented by a group of atoms whose electron “spins” all are oriented in a particular direction, creating a minute magnetic field. To change the bit from, say, a one to a zero, the drive’s write head imposes a field in a different direction at that point, causing the electrons to become magnetically excited. Their magnetic poles begin precessing—the same motion seen in a child’s spinning top when it’s tilted to one side and begins rotating around a vertical axis. Damping is what siphons off this energy, allowing the electron spins to settle into a new orientation. For fast write speeds—magnetization reversals in a nanosecond or faster—a hard disk wants strong damping.

On the other hand, damping is associated with noise and loss of signal in the same drive’s read heads—and other magnetic field sensors—so they need materials with very weak damping.

The design of improved magnetic devices, particularly at the nanoscale, requires a palette of materials with tailored damping rates, but unfortunately the damping mechanism is not well understood. Important damping mechanisms have not been identified, particularly for the so-called intrinsic damping seen in pure ferromagnetic materials, and no quantitative calculations of the damping rate have been done, so the search for improved materials must be largely by trial and error.

To address this, CNST researchers calculated the expected damping parameters for three commonly used ferromagnetic elements, iron, cobalt and nickel, based on proposed models that link precession damping in a complex fashion with the creation of electron-hole pairs in the metal that ultimately dissipate the magnetic excitation energy as vibration energy in the crystal structure. The calculation is extremely complex, both because of the intrinsic difficulty of accounting for the mutual interactions of large numbers of electrons in a solid, and because the phenomenon is inherently complex, with at least two different and competing mechanisms. Damping rises with temperature in all three metals, for example, but in cobalt and nickel it also rises with decreasing temperature at low temperatures.

By comparing the calculated damping effects with experimental measurements, the team was able to identify the dominant mechanisms behind intrinsic damping in the three metals, which at room temperature and above is tied to electron energy transitions. The results, they say, point to materials design techniques that could be used to optimize damping in new magnetic alloys.

Michael Baum | EurekAlert!
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht Quantum optical sensor for the first time tested in space – with a laser system from Berlin
23.01.2017 | Ferdinand-Braun-Institut Leibniz-Institut für Höchstfrequenztechnik

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

Quantum optical sensor for the first time tested in space – with a laser system from Berlin

23.01.2017 | Physics and Astronomy

The interactome of infected neural cells reveals new therapeutic targets for Zika

23.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>