Diamond wire seeded with nitrogen atoms has been proven to carry spin

Diamond may be promising material for spintronics

Information has been observed flowing through a diamond wire for the first time, opening the material up to use in the emerging field of ‘spintronics’.

Researchers have long held out hopes of exploiting both the intrinsic quantum property of spin in an electron and its associated magnetic moment – a measure of the object's tendency to align with a magnetic field – to transmit data in solid-state devices.

Now a new study carried out at the Ohio State University found that diamond wire transmits spin better than most metals in which researchers have previously observed the effect.

In the experiment electrons did not flow through the diamond, as they do in traditional electronics, but instead stayed in place and passed on their spin sates to each other down the wire – like football fans doing a ‘Mexican Wave’.

Added to the fact that diamond is already hard, transparent, electrically insulating, impervious to environmental contamination, resistant to acids, and doesn't hold heat as semiconductors do, the material appears to be promising for use in the emerging field according to lead investigator Professor Chris Hammel.

"Basically, it's inert. You can't do anything to it. To a scientist, diamonds are kind of boring, unless you're getting engaged," he said. "But it's interesting to think about how diamond would work in a computer."

Normally diamond couldn't carry spin as its carbon atoms are locked together with each electron firmly attached to a neighbouring electron, so the researchers had to seed the wire with nitrogen atoms in order for there to be unpaired electrons that could spin.

Despite the findings, the fact that the team had to chill the wire to 4.2 Kelvin means hopes of creating a diamond transistor are a long way off, but Hammel says the discovery, published in the journal Nature Nanotechnology yesterday, could change the way researchers study spin.

Electrons attain different spin states according to the direction in which they're spinning – up or down. Hammel's team placed a tiny diamond wire in a magnetic resonance force microscope and detected that the spin states inside the wire varied according to a pattern.

"If this wire were part of a computer, it would transfer information. There's no question that you'd be able to tell at the far end of the wire what the spin state of the original particle was at the beginning," he said.

Surprisingly the scientists discovered that the spin states lasted twice as long near the end of the wire than in the middle – based on ordinary experiments, the physicists would expect spin states to last for the same length of time, regardless of where the measurement was made.

When they focused their microscope on the tip of the wire, they witnessed spin flowing in the only direction it could flow – into the wire – but when they panned along the wire to observe the middle, they noticed it emptied of spin twice as fast, because the spin states could flow in both directions – into and out of the wire.

"It's a dramatically huge effect that we were not anticipating," Hammel said. "The fact that spins can move like this means that the conventional way that the world measures spin dynamics on the macroscopic level has to be reconsidered – it's actually not valid.”

Conventional experiments can only detect the average spin state – how many electrons in the sample are pointing up, and how many are pointing down – the difference between knowing that an average of one quarter of football fans in a stadium are standing at any one time, and knowing that individual people are standing and sitting in a pattern timed to form a ‘Mexican Wave’.

"It's not the average we want," Hammel said. "We want to know how much the spins vary, and what is the lifetime of any particular spin state."

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