Power/Performance Bits: Sept. 27

Self-organizing circuits; pairing electric and magnetic materials.

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Self-organizing circuits

Researchers studying the behavior of nanoscale materials at the Department of Energy’s Oak Ridge National Laboratory discovered that due an unusual feature of certain complex oxides called phase separation, individual nanoscale regions can behave as self-organized circuit elements, which could support new multifunctional types of computing architectures.

“Within a single piece of material, there are coexisting pockets of different magnetic and/or electronic behaviors,” said ORNL’s Zac Ward, the study’s corresponding author. “What was interesting in this study was that we found we can use those phases to act like circuit elements. The fact that it is possible to also move these elements around offers the intriguing opportunity of creating rewritable circuitry in the material.”

Because the phases respond to both magnetic and electrical fields, the material can be controlled in multiple ways, which creates the possibility for new types of computer chips.

An ORNL study found that complex oxide materials can self-organize into electrical circuits, which creates the possibility for new types of computer chips. (Source: ORNL)

An ORNL study found that complex oxide materials can self-organize into electrical circuits, which creates the possibility for new types of computer chips. (Source: ORNL)

“It’s a new way of thinking about electronics, where you don’t just have electrical fields switching off and on for your bits,” Ward said. “This is not going for raw power. It’s looking to explore completely different approaches towards multifunctional architectures where integration of multiple outside stimuli can be done in a single material.”

“Typically you would need to link several different components together on a computer board if you wanted access to multiple outside senses,” Ward said. “One big difference in our work is that we show certain complex materials already have these components built in, which may cut down on size and power requirements.”

The team aims to increase performance by developing hardware around intended applications. Said Ward, “This means that materials and architectures driving supercomputers, desktops, and smart phones, which each have very different needs, would no longer be forced to follow a one-chip-fits-all approach.”

Pairing electric and magnetic materials

In the search for ultra-low power electronics, scientists at the Lawrence Berkeley National Laboratory and Cornell University successfully paired ferroelectric and ferrimagnetic materials so that their alignment can be controlled with a small electric field at near room temperatures.

One path to reducing energy consumption involves ferroic materials. Key advantages of ferroelectrics include their reversible polarization in response to low-power electric fields, and their ability to hold their polarized state without the need for continuous power.

“If you look at this in a broad sense, about 5% of our total global energy consumption is spent on electronics,” said Ramamoorthy Ramesh, Berkeley Lab’s Associate Laboratory Director for Energy Technologies and a UC Berkeley professor of materials science and engineering and of physics. “It’s the fastest growing consumer of energy worldwide. The Internet of Things is leading to the installation of electronic devices everywhere. The world’s energy consumed by microelectronics is projected to be 40-50 percent by 2030 if we continue at the current pace and if there are no major advances in the field that lead to lower energy consumption.”

The researchers found that by manipulating films of hexagonal lutetium iron oxide (LuFeO3), a robust ferroelectric, they could dramatically change the material’s properties and produce a strongly ferrimagnetic layer near room temperature.

The researchers use electric fields to create concentric boxes of "up" and "down" ferroelectric polarization (shown left in red and turquoise) in the lutetium ferrite film. They then use photo emission electron microscopy at the Advanced Light Source to read out the magnetic structure from this region, demonstrating that the magnetism directly tracks the ferroelectric structure even though no magnetic fields were applied. The scale bar is 5 microns. (Source: James Clarkson, Alan Farhan, and Andreas Scholl/Berkeley Lab)

The researchers use electric fields to create concentric boxes of “up” and “down” ferroelectric polarization (shown left in red and turquoise) in the lutetium ferrite film. They then use photo emission electron microscopy at the Advanced Light Source to read out the magnetic structure from this region, demonstrating that the magnetism directly tracks the ferroelectric structure even though no magnetic fields were applied. The scale bar is 5 microns. (Source: James Clarkson, Alan Farhan, and Andreas Scholl/Berkeley Lab)

Under testing, the new material showed that the ferrimagnetic atoms followed the alignment of their ferroelectric neighbors when switched by an electric field. This happened in temperatures ranging from 200-300 kelvins (-100 to 80 degrees Fahrenheit). Other such multiferroics typically work at much lower temperatures.

“It was when our collaborators at Berkeley Lab demonstrated electrical control of magnetism in the material that we made that things got super exciting!” said Darrell Schlom, a professor of materials science and engineering at Cornell. “Room-temperature multiferroics are rare. Including our new material, a total of four are known, but only one room-temperature multiferroic was known in which magnetism could be controlled electrically. Our work shows that an entirely different mechanism is active in this new material, giving us hope for even better — higher temperature and stronger — manifestations for the future.”

The researchers next plan to explore strategies for lowering the voltage threshold for influencing the direction of polarization. This includes experimenting with different substrates for building new materials. “We want to show that this works at half a volt as well as at 5 volts,” said Ramesh. “We also want to make a working device with the multiferroic.”

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