Single-molecule magnet images at the nanoscale


Rebecca Pool

Thursday, May 16, 2019 - 19:30
STM imaging from weak to strong spin interactions between two magnetic molecules. [Wilson Ho]
A team of US- and China-based researchers have used scanning probe microscopy to develop a single-molecule sensor that can measure and image magnetic structures and interactions on the atomic-scale in unprecedented detail.
Representing a huge breakthrough for magnetic single atom and molecule research, the spin-sensing probe is set to fuel the development of magnetic memory storage, spintronic and quantum computing applications.
Single molecule SPM tips are being increasingly used as sensors to detect and image short-range and electrostatic forces between molecules.
“There is now a pressing need to develop techniques that can follow spin systems interacting with the local environment,” write Professor Wilson Ho from the University of California Irvine, and colleagues from Irvine and Fudan University, in Science. “Scanning probe microscopy techniques offer particular experimental advantages... but the use of magnetic molecule tips as sensors of local magnetic fields or spin-spin interactions has rremained challenging.”
Given this, Ho and colleagues set out to create a new approach based on the single molecule, nickelocene. 
Here, they attached the molecule to the probe tip of their custom-build, ultra-high vacuum scanning probe microscope to create a single-molecule sensor.
They then used this sensor to investigate the spin-spin interactions between its nickelocene molecule and a second nickelocene molecule adsorbed on a silver surface.
On moving the probe tip towards the adsorbed nickelocene, they could detect the magnetic and spin interactions between the magnetic molecules and went on to image the contours of these interactions in three spatial directions.
STM imaging from weak to strong spin interactions between two magnetic molecules. [Wilson Ho]
As Ho points out, analyses revealed angstrom-scale regions where the quantum states of the two magnetic molecules strongly mixed.
“Our results pave the way for new nanoscale imaging capabilities based on magnetic single-molecule sensors,” he says. “Analogous to the force-sensing capabilities of carbon-monoxide-terminated tips that have become commonplace to image chemical structures on surfaces, we anticipate that spin-sensing probes based on single magnetic molecules will become widely adopted.”
Research is published in Science.
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