Researchers from the Division of Energy’s Ames Public Lab made a charming revelation while leading tests to portray attraction in a material known as a weakly attractive topological separator where attractive imperfections are presented. The team discovered strong antiferromagnetic interactions between some pairs of magnetic defects that are essential to several families of magnetic topological insulators, despite the material’s ferromagnetism.
Topological separators (TIs), as their name demonstrates, are covers. However, under the right conditions, they can conduct electricity on the surface due to their distinctive electronic band structure. TIs are capable of transmitting electrical currents without generating heat or wasting energy by introducing magnetism. Because of this quality, they have the potential to reduce computing and electricity transmission’s energy consumption in the future.
As per Burglarize McQueeney, a researcher from Ames Lab and an individual from the exploration group, “It isn’t so natural to track down topological separators. You have to locate this one-of-a-kind circumstance in which the electronic bands are tangled up.” He went on to explain that a TI’s surface transforms into a one-of-a-kind two-dimensional insulator when a magnetic field is applied, while the edges of the surface remain metallic.
“It is not easy to find topological insulators. You must find this one-of-a-kind condition in which the electronic bands are entangled.”
Rob McQueeney, a scientist from Ames Lab and a member of the research team,
A ferromagnetic TI is a crucial objective. When all of a material’s magnetic moments spontaneously align in the same direction, this is known as ferromagnetism. However, the team also discovered that when defects are introduced, TIs are susceptible to antiferromagnetic interactions. When some of the ions naturally align with other ions that are nearby, this is known as antiferromagnetism. The material’s overall magnetism is lowered by the opposing magnetic forces.
There are two different ways that researchers bring attraction to a TI. The first is to introduce small amounts of magnetic ions, like antimony telluride or bismuth telluride that has been doped with manganese. The second method is to insert a layer of magnetic ions, such as manganese-antimony-tellurium (MnSb2Te4), into the material to create an intrinsic magnetic TI.
The intrinsic magnetic TIs have a complete layer of magnetic ions, so the magnetism should not be distributed randomly like it is in the first method.
For this undertaking, the group zeroed in on weakening attractive TIs, which have arbitrarily conveyed attractive deformities. ” We wanted to comprehend the most fundamental aspects of magnetic interactions. Farhan Islam, a graduate student at Iowa State University and a member of the team, stated, “We were doping our sample using small amounts of magnetic ions to try to understand how the magnetic interactions occur.” So, basically, we’re trying to figure out how the system’s overall magnetism is affected by interactions at the microscopic level.”
To lead their exploration, the group utilized a particular technique called neutron dissipating. A sample of material is passed through a beam of neutrons, which are neutral-charged subatomic particles. By keeping track of where and when the sample’s neutrons hit a detector, data can be gathered.
This sort of exploration must be done in a couple of spots on the planet. For this project, the Oak Ridge National Laboratory’s Spallation Neutron Source, a Department of Energy Office of Science User Facility, was used for neutron scattering.
The weak signal of neutron scattering presents a challenge. The group had worries about concentrating on weakening attraction due to the relatively small number of attractive particles. “I was extremely distrustful that we would see anything by any means,” said McQueeney. “We just did. Surprisingly, what we saw was actually fairly straightforward to observe.”
Some isolated pairs of magnetic defects in manganese-doped antimony telluride (Sb1.94Mn0.06Te3) are antiferromagnetically coupled with opposite moment directions, despite the material’s overall ferromagnetism, the researchers discovered. Ferromagnetically coupled with parallel moments are other magnetic pairs, particularly those in distinct blocks of the layered structure. The competing attractive powers diminish the general attraction of the material.
Islam explained, “The intrinsic magnetic TIs actually have defects.” Manganese, for instance, is able to enter antimony deposits in places where it is prohibited, and the manner in which it does so is arbitrary.
The intrinsic magnetic TIs develop magnetic defects as a result of this random manganese site mixing. The team discovered that intrinsic materials (MnSb2Te4) also have the same interactions between defects as dilute materials. The attractive ground condition of the inborn attractive TIs can be either ferromagnetic or antiferromagnetic, and the group currently comprehends how attractive deformities control this way of behaving.
McQueeney stated, “We discovered that these interactions are transferable to the intrinsic case and determined the interactions between defects in the dilute case.” We conclude that defects control the magnetic order for both families by doing so.
The review is distributed in the diary as “Progressed Materials.
More information: Farhan Islam et al, Role of Magnetic Defects in Tuning Ground States of Magnetic Topological Insulators, Advanced Materials (2023). DOI: 10.1002/adma.202209951
