Wednesday , April 21 2021

Tech: Unprecedented insight into two-dimensional magnets using diamond quantum sensors – (Report)



For the first time, physicists at the University of Basel have been able to measure the magnetic properties of atomically thin van der Waals materials on a nano. They used diamond quantum sensors to determine the magnetization strength of the individual atomic layers of the material chromium triiodide. In addition, they found a long request explanation for the unusual magnetic properties of the material. The magazine Science published the findings.

The use of atomically thin, two-dimensional van der Waals materials promises innovation in many areas of science and technology. Scientists around the world are constantly exploring new ways of acquiring different single atomic layers and thus creating new materials with unique, new properties.

These super-thin composite materials are maintained together with van der Waals forces and often behave differently to large crystals of the same material. Atomic thin van der Waals materials include insulators, semiconductors, superconductors, and several materials with magnetic properties. Their use in spintronics or ultra-compact magnetic memory media is very promising.

The first quantitative measurement of magnetization

Until now, it is not possible to determine the strength, consistency and structure of these magnets in the quantitative or the nanomaterial. The team led by Professor Georg-H.-Andres Patrick Maletinski of the Department of Physics and the Swiss Institute of Nanotechnology at the University of Basel have shown that the use of diamond tips adorned with one electronic spin in a microscope with atomic force is perfectly suited for these types of studies.

"Our method, which uses individual spinning in diamond-colored centers as sensors, opens a new field. The magnetic properties of two-dimensional materials can now be studied on nanomaterials, even in a quantitative way." Our innovative quantum sensors are perfectly suited for this complex task, "said Maletinski.

The number of layers is critical

Using this technology originally developed in Basel and based on an electronic spin, scientists collaborated with researchers at the University of Geneva to determine the magnetic properties of single atomic layers of chromium triiodide (CrI3). The researchers could thus find the answer to the key scientific questions about the magnetism of this material.

As a three-dimensional, most of the crystal, the chromium triiodide is completely magnetically ordered. In the case of several atomic layers, however, only piles with an odd number of atomic layers show unnecessary magnetization. Stacks with a pair of layers show antiferromagnetic behavior; that is, they are not magnetized. The reason for this "honest / odd effect" and the discrepancy between the material material was previously unknown.

Virus as a cause

The Maletinski team could have shown that this phenomenon is due to the specific atomic layers of the layers. During the preparation of the sample, the individual chromium triiodide layers are slightly moving against one another. The resulting pressure in the grid means that the rotations of successive layers can not be aligned in the same direction; Instead, the direction of rotation changes in layers. With a pair of layers, the reduction of the magnetization of the layers; with an odd number, the magnitude of the measured magnetization corresponds to that of one layer.

However, when the virus is released into the stack – for example, by penetrating the sample – the rotations of all the layers can be aligned in the same direction as is observed in the mass crystals. The magnetic strength of the entire stack then is in line with the sum of the individual layers.

The work of Basel's scientists not only answers key questions for two-dimensional van der Waals magnets, but also opens up interesting perspectives on how their innovative quantum sensors can be used in the future to study two-dimensional magnets in order to contribute for the development of new electronic components.


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