An international research collaboration, including The University of Warwick, The University of Cambridge and UCL, has demonstrated that ‘wonder material’ phosphorene nanoribbons (PNRs) exhibit both magnetic and electronic properties at room temperature, establishing them as a unique class of low-dimensional materials.

Scientists have long suspected that phosphorene nanoribbons (PNRs) – thin pieces of black phosphorus, only a few nanometres wide – might exhibit unique magnetic and semiconducting properties, making them a valuable material.  

For the first time, using advanced techniques such as ultrafast magneto-optical spectroscopy and electron paramagnetic resonance, this Nature study has shown PNRs to have these properties at room temperature. 

Raj Pandya, Assistant Professor at The University of Warwick and corresponding author said: “Phosphorene nanoribbons have long been predicted to have fascinating magnetic and electronic properties for a plethora of applications (catalysis, energy storage, computing), but testing these has been a challenge. It is really great to see that these properties do indeed exist providing a stepping stone towards new and improved technological devices.” 

Remarkably, these nanoribbons exhibit macroscopic magnetic properties at room temperature. Under relatively weak magnetic fields (<1T) they surprisingly stand at attention in solution almost like iron filings arrange themselves around a magnet. Furthermore, when in thin films they can display macroscopic magnetic behaviour akin only to that of classic magnetic metals such as iron and nickel.  

Arjun Ashoka, Junior Research Fellow at Trinity College, University of Cambridge and the first author added: “Most excitingly, we discovered that in addition to these magnetic properties, PNRs host excited states on the magnetic edge of the nanoribbon, where it interacts with atomic vibrations (phonons) that are normally not allowed by the material’s bulk symmetries. This unusual interaction allows PNRs to uniquely couple magnetic, optical and vibrational properties on its one-dimensional edge. 

"For years we've explored and utilised the devilish yet benevolent 2D surfaces of 3D materials, from catalysis to device physics. With these new nanoribbons we've hopefully unlocked access to new physics on the 1-dimensional analogue of a 2D surface: an edge."  

This work marks the first experimental validations of the predicted, but difficult to observe, magnetic properties of phosphorene nanoribbons. It challenges conventional views on magnetic semiconductors and could provide a stepping stone to unlocking new quantum technologies. 

“The confirmation that phosphorene nanoribbons are intrinsically both semiconducting and magnetic—without requiring low temperatures or doping—is particularly important and novel. While this property was predicted, directly observing it is an incredible validation of those predictions," adds Professor Chris Howard from University College London whose team first synthesised these nanoribbons.  

This research could influence multiple avenues of science and technology. It could enable new routes to spintronic devices, which use electron spin instead of charge, to enable novel computing technologies such as scalable fabrication for quantum devices, flexible electronics and next generation transistors.  

ENDS  
 
Notes to Editors  

On Phosphorene Nanoribbons:  

Phosphorene is a mono-elemental, two-dimensional (2D) substance with outstanding, highly directional properties and a bandgap that depends on the number of layers of the material. Nanoribbons, meanwhile, combine the flexibility and unidirectional properties of one-dimensional nanomaterials, the high surface area of 2D nanomaterials and the electron-confinement and edge effects of both. The structures of nanoribbons can thus lead to exceptional control over electronic band structure, the emergence of novel phenomena and unique architectures for applications. Phosphorene’s intrinsically anisotropic structure has motivated numerous theoretical calculations of phosphorene nanoribbons (PNRs), predicting extraordinary properties. (Sourced from: Watts, M.C., Picco, L., Russell-Pavier, F.S. et al. Production of phosphorene nanoribbons. Nature 568, 216–220 (2019). https://doi.org/10.1038/s41586-019-1074-x)

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