Ferrimagnetic materials make spintronic memory more stable

Monday, 17 December, 2018

Ferrimagnetic materials make spintronic memory more stable

A research team led by the National University of Singapore (NUS) has invented a magnetic memory device which is able to manipulate digital information 20 times more efficiently and with 10 times more stability than commercial spintronic digital memories.

Spearheaded by Associate Professor Hyunsoo Yang, the spintronic device was developed in collaboration with the Toyota Technological Institute and Korea University. It has been described in the journal Nature Materials.

With digital information being generated in unprecedented amounts, there is an increasing demand for low-cost, low-power, highly stable and highly scalable memory and computing products. One way this is being achieved is with new spintronic materials, where digital data are stored in up or down magnetic states of tiny magnets. However, while existing spintronic memory products based on ferromagnets succeed in meeting some of these demands, they are still very costly due to scalability and stability issues.

“Ferromagnet-based memories cannot be grown beyond a few nanometres thick, as their writing efficiency decays exponentially with increasing thickness,” explained Dr Yu Jiawei, who was involved in the project while pursuing her doctoral studies at NUS. “This thickness range is insufficient to ensure the stability of stored digital data against normal temperature variations.”

To address these challenges, the team fabricated a magnetic memory device using an interesting class of magnetic material — ferrimagnets. Crucially, it was discovered that ferrimagnetic materials can be grown 10 times thicker without compromising on the overall data writing efficiency.

“The spin of the current-carrying electrons, which basically represents the data you want to write, experiences minimal resistance in ferrimagnets,” said research team member Rahul Mishra. “Imagine the difference in efficiency when you drive your car on an eight-lane highway compared to a narrow city lane. While a ferromagnet is like a city street for an electron’s spin, a ferrimagnet is a welcoming freeway, where its spin or the underlying information can survive for a very long distance.”

Using an electronic current, the researchers were able to write information in a ferrimagnet memory element which was 10 times more stable and 20 times more efficient than a ferromagnet. This was made possible due to the unique atomic arrangement in a ferrimagnet.

“In ferrimagnets, the neighbouring atomic magnets are opposite to each other,” Assoc Prof Yang said. “The disturbance caused by one atom to an incoming spin is compensated by the next one, and as a result information travels faster and further with less power. We hope that the computing and storage industry can take advantage of our invention to improve the performance and data retention capabilities of emerging spin memories.”

The research team is now planning to look into the data writing and reading speed of their device, as they expect its distinctive atomic properties will also result in ultrafast performance. They are also planning to collaborate with industry partners to accelerate the commercial translation of their discovery.

“Our discovery could provide a new device platform to the spintronic industry,” Assoc Prof Yang said.

Image caption: A team led by Assoc Prof Hyunsoo Yang (second from left) has discovered that ferrimagnet devices can manipulate digital information more efficiently and with more stability than commercial spintronic digital memories.

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