Capture of nanomagnetic 'fingerprints' a boost for next-generation information storage media

Jan 29, 2009
This magnetic fingerprint, or "FORC distribution," of 10-nanometer-thick cobalt nanodisks shows that all the magnetic moments are pointing in the same direction. Credit: Kai Liu/UC Davis

In the race to develop the next generation of storage and recording media, a major hurdle has been the difficulty of studying the tiny magnetic structures that will serve as their building blocks. Now a team of physicists at the University of California, Davis, has developed a technique to capture the magnetic "fingerprints" of certain nanostructures - even when they are buried within the boards and junctions of an electronic device.

This breakthrough in nanomagnetism was published in the Jan. 19 issue of Applied Physics Letters.

The past decade has witnessed a thousand-fold increase in magnetic recording area density, which has revolutionized the way information is stored and retrieved. These advances are based on the development of nanomagnet arrays which take advantage of the new field of spintronics: using electron spin as well as charge for information storage, transmission and manipulation.

But due to the miniscule physical dimensions of nanomagnets - some are as small as 50 atoms wide - observing their magnetic configurations has been a challenge, especially when they are not exposed but built into a functioning device.

"You can't take full advantage of these nanomagnets unless you can 'see' and understand their magnetic structures - not just how the atoms and molecules are put together, but how their electronic and magnetic properties vary accordingly," said Kai Liu, a professor and Chancellor's Fellow in physics at UC Davis. "This is difficult when the tiny nanomagnets are embedded and when there are billions of them in a device."

To tackle this challenge, Liu and three of his students, Jared Wong, Peter Greene and Randy Dumas, created copper nanowires embedded with magnetic cobalt nanodisks. Then they applied a series of magnetic fields to the wires and measured the responses from the nanodisks. By starting each cycle at full saturation - that is, using a field strong enough to align all the nanomagnets - then applying a progressively more negative field with each reversal, they created a series of information-rich graphic patterns known to physicists as "first-order reversal curve (FORC) distributions."

"Each pattern tells us a different story about what's going on inside the nanomagnets," Liu said. "We can see how they switch from one alignment to another, and get quantitative information about how many nanomagents are in one particular phase: for example, whether the magnetic moments are all pointing in the same direction or curling around a disk to form vortices. This in turn tells us how to encode information with these nanomagnets."

The technique will be applicable to a wide variety of physical systems that exhibit the kind of lag in response time (or hysteresis) as magnets, including ferroelectric, elastic and superconducting materials, Liu explained. "It's a powerful tool for probing variations, or heterogeneity, in the system, and real materials always have a certain amount of this."

Source: University of California - Davis

Explore further: Throwing light on a mysterious human 'superpower'

add to favorites email to friend print save as pdf

Related Stories

Stanford pair helping predict solar storms

Feb 19, 2015

Life as a forecaster is not easy. Just ask National Weather Service forecasters who misjudged how a recent winter storm would impact the Big Apple. Now imagine trying to predict weather activity on a burning ...

Recommended for you

Throwing light on a mysterious human 'superpower'

2 hours ago

Most people, at some point in their lives, have dreamt of being able to fly like Superman or develop superhuman strength like the Hulk. But very few know that we human beings have a "superpower" of our own, ...

New filter could advance terahertz data transmission

Feb 27, 2015

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

Feb 27, 2015

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

A new X-ray microscope for nanoscale imaging

Feb 27, 2015

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

holoman
not rated yet Jan 29, 2009
Oops, now they are moving into ferroelectrics and multiferroics because ferromagnetics is dead.

What they propose is ancient history.

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.