Nav: Home

Unprecedented insight into two-dimensional magnets using diamond quantum sensors

April 25, 2019

For the first time, physicists at the University of Basel have succeeded in measuring the magnetic properties of atomically thin van der Waals materials on the nanoscale. They used diamond quantum sensors to determine the strength of the magnetization of individual atomic layers of the material chromium triiodide. In addition, they found a long-sought explanation for the unusual magnetic properties of the material. The journal Science has published the findings.

The use of atomically thin, two-dimensional van der Waals materials promises innovations in numerous fields in science and technology. Scientists around the world are constantly exploring new ways to stack different single atomic layers and thus engineer new materials with unique, emerging properties.

These super-thin composite materials are held together by van der Waals forces and often behave differently to bulk crystals of the same material. Atomically thin van der Waals materials include insulators, semiconductors, superconductors and a few materials with magnetic properties. Their use in spintronics or ultra-compact magnetic memory media is highly promising.

The first quantitative measurement of magnetization

Until now, it has not been possible to determine the strength, alignment and structure of these magnets quantitatively nor on the nanoscale. The team headed by Georg-H.-Endress Professor Patrick Maletinsky from the Department of Physics and the Swiss Nanoscience Institute at the University of Basel have demonstrated that the use of diamond tips decorated with single electron spins in an atomic force microscope is ideally suited to these types of studies.

"Our method, which uses the individual spins in diamond color centers as sensors, opens up a whole new field. The magnetic properties of two-dimensional materials can now be studied on the nanoscale and even in a quantitative manner. Our innovative quantum sensors are perfectly suited to this complex task," says Maletinsky.

The number of layers is critical

Using this technology which was originally developed in Basel and which is based on a single electron spin, the scientists collaborated with researchers from the University of Geneva to determine the magnetic properties of single atomic layers of chromium triiodide (CrI3). The researchers were thus able to find the answer to a key scientific question about the magnetism of this material.

As a three-dimensional, bulk crystal, chromium triiodide is fully magnetically ordered. In the case of few atomic layers, however, only stacks with an odd number of atomic layers show a non-zero magnetization. Stacks with an even number of layers exhibit an antiferromagnetic behavior; i.e. they are not magnetized. The cause of this "even/odd-effect" and the discrepancy to bulk material was previously unknown.

Strain as the cause

Maletinsky's team was able to demonstrate that this phenomenon is due to the specific atomic arrangement of the layers. During sample preparation, the individual chromium triiodide layers slightly move against one another. The resulting strain in the lattice means the spins of successive layers are unable to align in the same direction; instead, the spin direction alternates in the layers. With an even number of layers, the magnetization of the layers cancel out; with an odd number, the strength of the measured magnetization corresponds to that of a single layer.

However, when the strain in the stack is released - for example, by puncturing the sample - the spins of all layers can align in the same direction, as is also observed in bulk crystals. The magnetic strength of the entire stack is then consistent with the sum of the individual layers.

The work conducted by the Basel scientists thereby not only answers a key question about two-dimensional van der Waals magnets, it also opens interesting perspectives on how their innovative quantum sensors can be used in the future to study two-dimensional magnets in order to contribute to the development of novel electronic components.
-end-


University of Basel

Related Sensors Articles:

Sensors detect disease markers in breath
A small, thin square of an organic plastic that can detect disease markers in breath or toxins in a building's air could soon be the basis of portable, disposable sensor devices.
Are your sensors spying on you?
Cyber experts at Newcastle University, UK, have revealed the ease with which malicious websites and installed apps can spy on us using just the information from the motion sensors in our mobile phones.
A novel method for the fabrication of active-matrix 3-D pressure sensors
A new study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST), developed a transistor-type active-matrix pressure sensor using foldable substrate and air-dielectric layer.
For female mosquitoes, two sets of odor sensors are better than one
A team of Vanderbilt biologists has found that the malaria mosquito has a second complete set of odor receptors that are specially tuned to human scents.
Optimized sensors to study learning and memory
Scientists at Max Planck Florida Institute for Neuroscience are working to understand how molecules send messages throughout the neuron.
Pioneering chip extends sensors' battery life
A low-cost chip that enables batteries in sensors to last longer, in some cases by over ten times, has been developed by engineers from the University of Bristol.
New sensors can detect single protein molecules
For the first time, MIT engineers have designed sensors that can detect single protein molecules as they are secreted by cells.
Contracts signed for ELT mirrors and sensors
At a ceremony today at ESO's Headquarters four contracts were signed for major components of the Extremely Large Telescope (ELT) that ESO is building.
Pain sensors specialized for specific sensations
Many pain-sensing nerves in the body are thought to respond to all types of 'painful events', but new UCL research in mice reveals that in fact most are specialized to respond to specific types such as heat, cold or mechanical pain.
3-D-printed organ-on-a-chip with integrated sensors
Researchers have made the first entirely 3-D-printed organ-on-a-chip with integrated sensing.

Related Sensors Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".