Spintronic Materials Show Their First Move

Mar 23, 2005

How much energy does it take for an electron to hop from atom to atom, and how do the magnetic properties of the material influence the rate or ease of hopping? Answers to those questions could help explain why some materials, like those used in a computer hard drive, become conductors only in a magnetic field while they are very strong insulators otherwise. They might also help scientists learn how to use the electron’s "spin", as well as its charge, to carry information in a new field known as spintronics.

Stéphane Grenier, a postdoctoral fellow studying electronic excitations, or “electron hopping,” at the U.S. Department of Energy’s Brookhaven National Laboratory, described the techniques he used and the properties of these materials at the March 2005 meeting of the American Physical Society in Los Angeles, California.

“We are looking at something very local, electrons hopping between a pair of atoms, to help us understand important macroscopic effects,” Grenier says. “This information could help predict which materials might have the properties needed for particular applications — say, increasing the storage capacity of computer hard drives — and direct the fabrication of new materials in which these properties are optimized.”

To determine the energy needed by an electron to hop from one atom to another atom, Grenier used a technique called inelastic x-ray scattering at the Advanced Photon Source at Argonne National Laboratory. He shines x-ray light onto the sample and measures the tiny difference in energy between the incoming and outgoing photons. This difference is the amount of energy needed to move the electrons.

He used this technique to study materials with different magnetic “lattices” — ferromagnetic and antiferromagnetic. In ferromagnetic materials, the atoms’ magnetic moments (that is, their spins) are all aligned in the same direction. In antiferromagnetic materials, the magnetic moments of the adjacent atoms point in opposite directions. “When the magnetic moments are aligned, the electron hopping is increased between particular atoms. That is, more electrons make the jump to their neighbors, and it takes less energy to move them,” Grenier says. “While this has been known for a while, we have shown the direction in which the electrons move and exactly what price they ‘pay,’ in terms of energy, to move, and the influence the magnetic lattice of the material has on this hopping.”

The electrons want to align their own magnetic moments, or spins, with that of the atoms in the lattice, he explains. “They will do so only if all the atoms’ magnetic moments are aligned — that is when the ‘fare’ for hopping has its lowest price,” he said.

Electrons moving with their spins aligned in the same direction make a current of spins, which could be used, somewhat like currents of electrical charge are now used, to pass or transform information in future electronic components made of tailored magnetic lattices — a future generation of circuits based on the science of “spintronics,” which is also carried out at Brookhaven Lab. Grenier’s studies, along with theoretical analysis of the materials, may also help scientists understand why some materials possess properties such as superconductivity and “colossal magnetoresistance,” the ability of some strong insulators to become good conductors when induced by a magnetic field.

Studies on atomic magnetism have applications for understanding novel materials — including spintronic materials and superconductors — that will revolutionize the electronic and energy industries. Such studies using x-rays can only be performed in the U.S. at x-ray synchrotron radiation facilities built and managed by the U.S. Department of Energy’s Office of Science.

This research was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy’s Office of Science.

Source: Brookhaven National Laboratory

Explore further: Generating broadband terahertz radiation from a microplasma in air

Related Stories

Electrons move like light in three-dimensional solid

Apr 22, 2015

Electrons were observed to travel in a solid at an unusually high velocity, which remained the same independent of the electron energy. This anomalous light-like behavior is found in special two-dimensional ...

Putting a new spin on computing memory

Apr 22, 2015

Ever since computers have been small enough to be fixtures on desks and laps, their central processing has functioned something like an atomic Etch A Sketch, with electromagnetic fields pushing data bits ...

Giant magnetic effects induced in hybrid materials

Apr 21, 2015

Proximity effects in hybrid heterostructures, which contain distinct layers of different materials, allow one material species to reveal and/or control properties of a dissimilar species. Specifically, for ...

Ultrafast tracking of electron spins

Apr 21, 2015

Our present digital information processing and storage is based on two properties of the electron. The first is its charge, which is used in electronic circuits to process information. The second is its spin, ...

Recommended for you

Researchers build real-time tunable plasmon laser

Apr 24, 2015

(Phys.org)—A combined team of researchers from Northwestern and Duke Universities has succeeded in building a plasmon laser that is tunable in real-time. In their paper published in the journal Nature Co ...

Heat makes electrons spin in magnetic superconductors

Apr 24, 2015

Physicists have shown how heat can be exploited for controlling magnetic properties of matter. The finding helps in the development of more efficient mass memories. The result was published yesterday in Physical Review Le ...

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.