Spintronics: Exotic ferromagnetic order in two-dimensions


STM topography of a monolayer CrCl3 grown on Graphene/6H-SiC(0001). Inset, a magnified topography picture, which reveals the grain boundaries. Credit: Science

The thinnest supplies on the planet are solely a single atom thick. These sorts of two-dimensional or 2D supplies—corresponding to graphene, well-known as consisting of a single layer of carbon atoms—are inflicting an excessive amount of pleasure amongst analysis groups worldwide. This is as a result of these supplies promise uncommon properties that can not be obtained utilizing three-dimensional supplies. As a outcome, 2D supplies are opening the door to new purposes in fields corresponding to data and show expertise, in addition to for vital elements in extraordinarily delicate sensors.

Structures referred to as van-der-Waals monolayers are arousing explicit curiosity. These are combos of two or extra layers of various supplies which can be every solely a single atom thick, with the layers held to at least one one other by weak electrostatic van-der-Waals forces. By choosing the sort and sequence of fabric layers sure on this means, particular electrical, magnetic, and optical traits could be chosen and modified. However, scaled-up homogeneous deposition of particular person van-der-Waals layers having ferromagnetic properties has not but been achieved. Yet it’s exactly this type of magnetism on a bigger scale that’s notably vital for a number of potential purposes—corresponding to for a novel type of non-volatile reminiscence for instance.

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Scientists from the Max Planck Institute for Microstructure Physics in Halle, Germany, the ALBA synchrotron mild supply in Barcelona, Spain, and the Helmholtz-Zentrum Berlin have now succeeded for the primary time in making a uniform two-dimensional materials—and demonstrating an unique ferromagnetic habits inside it referred to as “easy-plane” magnetism.

An almost free-floating layer of chromium and chlorine

The researchers from Germany and Spain utilized chromium chloride (CrCl3) as a cloth, which resembles the corresponding compound fabricated from chromium and iodine in construction—however could be significantly extra sturdy. The workforce in Halle deposited a macro-scale monoatomic layer of this materials upon a graphene-coated silicon-carbide substrate utilizing molecular-beam epitaxy. The objective of the graphene was to cut back the interplay between chromium chloride and silicon carbide and thereby forestall the substrate from influencing the properties of the monoatomic CrCl3 layer. This was the important thing to accessing the elusive magnetic easy-plane anisotropy”, explains Dr. Amilcar Bedoya-Pinto, a researcher in Prof. Stuart Parkin’s group at the Max Planck Institute in Halle. “Essentially, we obtained an virtually free-floating, ultrathin layer that was solely sure to the graphene interlayer by weak van-der-Waals forces.”

The workforce’s objective was to reply the query of how the magnetic order in chromium chloride manifests itself when it consists of solely a single monoatomic layer. In its regular three-dimensional kind, the substance is antiferromagnetic. As a outcome, the magnetic moments of the atoms are oriented in reverse instructions in every layer—which makes the fabric seem non-magnetic in bulk. Theoretical concerns thus far steered that the magnetic ordering is misplaced or displays weak standard magnetisation when the fabric is decreased to a single atomic layer.

Precise measurements on the VEKMAG facility

However, scientists have now succeeded in disproving this—by taking an in depth have a look at the magnetic properties of the 2D materials. To achieve this, they used the distinctive capabilities of the VEKMAG vector magnet facility put in at HZB’s synchrotron radiation supply BESSY II. “Here it is possible to investigate samples using soft X-rays in a strong magnetic field—and at temperatures near absolute zero”, says Dr. Florin Radu, head of the workforce at HZB answerable for operations on the VEKMAG facility. “Those aspects makes the facility unique in the world”, provides the Berlin scientist. It enabled the workforce members from Halle to find out the orientation of particular person magnetic moments and to precisely distinguish between chromium and chlorine atoms.

During the measurements, the researchers noticed how ferromagnetic order shaped within the two-dimensional materials beneath a sure temperature, what is named the Curie temperature. “In the monoatomic chromium chloride layer, a phase transition characteristic of easy-plane magnets took place that had never been observed before in such a 2D material”, reviews Bedoya-Pinto.

Tailwind for the event of spintronics

The discovery not solely provides new insights into the magnetic habits of two-dimensional supplies. “We now also have an excellent platform for exploring a variety of physical phenomena that only exist in two-dimensional magnets”, Bedoya-Pinto is happy to say, corresponding to superfluid (lossless) transport of spin, which is a form of intrinsic angular momentum of electrons and different particles. These are the idea for a brand new type of information processing that—not like standard electronics—makes use of magnetic moments slightly than electrical expenses. Known as spintronics, that is at present revolutionizing information storage and knowledge processing. The new insights gained at HZB may enhance this growth.

Visualising atomic structure and magnetism of 2-D magnetic insulators

More data:
Amilcar Bedoya-Pinto et al, Intrinsic 2D-XY ferromagnetism in a van der Waals monolayer, Science (2021). DOI: 10.1126/science.abd5146

Spintronics: Exotic ferromagnetic order in two-dimensions (2021, November 1)
retrieved 1 November 2021
from https://phys.org/news/2021-11-spintronics-exotic-ferromagnetic-two-dimensions.html

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