Science Current Events | Science News |

Nano-layer of ruthenium stabilizes magnetic sensors

August 06, 2007

A layer of ruthenium just a few atoms thick can be used to fine-tune the sensitivity and enhance the reliability of magnetic sensors, tests at the National Institute of Standards and Technology (NIST) show.* The nonmagnetic metal acts as a buffer between active layers of sensor materials, offering a simple means of customizing field instruments such as compasses, and stabilizing the magnetization in a given direction in devices such as computer hard-disk readers.

In the NIST sensor design, ruthenium modulates interactions between a ferromagnetic film (in which electron "spins" all point in the same direction) and an antiferromagnetic film (in which different layers of electrons point in opposite directions to stabilize the device). In the presence of a magnetic field, the electron spins in the ferromagnetic film rotate, changing the sensor's resistance and producing a voltage output. The antiferromagnetic film, which feels no force because it has no net magnetization, acts like a very stiff spring that resists the rotation and stabilizes the sensor. The ruthenium layer (see graphic) is added to weaken the spring, effectively making the device more sensitive. This makes it easier to rotate the electron spins, and still pulls them back to their original direction when the field is removed.

NIST tests showed that thicker buffers of ruthenium (up to 2 nanometers) make it easier to rotate the magnetization of the ferromagnetic film, resulting in a more sensitive device. Thinner buffers result in a device that is less sensitive but responds to a wider range of external fields. Ruthenium layers thicker than 2 nm prevent any coupling between the two active films. All buffer thicknesses from 0 to 2 nm maintain sensor magnetization (even resetting it if necessary) without a boost from an external electrical current or magnetic field. This easily prevents demagnetization and failure of a sensor.

The mass-producible test sensors, made in the NIST clean room in Boulder, Colo., consist of three basic layers of material deposited on silicon wafers: The bottom antiferromagnetic layer is 8 nm of an iridium/manganese alloy, followed by the ruthenium buffer, and topped with 25 nm of a nickel/iron alloy. The design requires no extra lithography steps for the magnetic layers and could be implemented in existing mass-production processes. By contrast, the conventional method of modulating magnetoresistive sensors-capping the ends of sensors with magnetic materials-adds fabrication steps and does not allow fine-tuning of sensitivity. The new sensor design was key to NIST's recent development of a high-resolution forensic tape analysis system for the Federal Bureau of Investigation (see Magnetic Tape Analysis "Sees" Tampering in Detail).

* S.T. Halloran, F.C. da Silva, H.Z. Fardi and D.P. Pappas. Permanent-magnet-free stabilization and sensitivity tailoring of magneto-resistive field sensors, Journal of Applied Physics. August 1, 2007.

National Institute of Standards and Technology (NIST)

Related Ruthenium Current Events and Ruthenium News Articles

Scientific breakthrough can lead to cheaper and environmentally friendly solar cells
The hope is to develop efficient and environmentally friendly solar energy applications. Solar energy is an inexhaustible resource that we currently only utilise to a very limited extent. Researchers around the world are therefore trying to find new and more efficient ways to use the energy in sunlight.

A micro-supercapacitor with unmatched energy storage performance
A micro-supercapacitor made using a new electrode reached an energy density 1,000 times greater than existing electrochemical capacitors.

A new method of converting algal oil to transportation fuels
A new method of converting squalene, which is produced by microalgae, to gasoline or jet fuel, has been developed by the research group of Professor Keiichi Tomishige and Dr. Yoshinao Nakagawa from Tohoku University's Department of Applied Chemistry, and Dr. Hideo Watanabe from the University of Tsukuba.

Scientists see ripples of a particle-separating wave in primordial plasma
Scientists in the STAR collaboration at the Relativistic Heavy Ion Collider, a particle accelerator exploring nuclear physics and the building blocks of matter at the U.S. Department of Energy's Brookhaven National Laboratory, have new evidence for what's called a "chiral magnetic wave" rippling through the soup of quark-gluon plasma created in RHIC's energetic particle smashups.

Stinging nettle chemical improves cancer drug
A cancer drug could be made 50 times more effective by a chemical found in stinging nettles and ants, new research finds.

First scientific publication from data collected at NSLS-II
Just weeks after the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory, achieved first light, a team of scientists at the X-Ray Powder Diffraction (XPD) beamline tested a setup that yielded data on thermoelectric materials.

Transformations of diazo compounds catalyzed by environmentally benign iron complexes
Catalysis can be used to enhance the reactivity and selectivity of specific chemical transformations and decrease the amount of energy consumed by these processes.

Batteries included: A solar cell that stores its own power
Is it a solar cell? Or a rechargeable battery? Actually, the patent-pending device invented at The Ohio State University is both: the world's first solar battery.

How to make a 'perfect' solar absorber
The key to creating a material that would be ideal for converting solar energy to heat is tuning the material's spectrum of absorption just right: It should absorb virtually all wavelengths of light that reach Earth's surface from the sun - but not much of the rest of the spectrum, since that would increase the energy that is reradiated by the material, and thus lost to the conversion process.

Improved Supercapacitors for Super Batteries, Electric Vehicles
Researchers at the University of California, Riverside have developed a novel nanometer scale ruthenium oxide anchored nanocarbon graphene foam architecture that improves the performance of supercapacitors, a development that could mean faster acceleration in electric vehicles and longer battery life in portable electronics.
More Ruthenium Current Events and Ruthenium News Articles

© 2015