ADVERTISEMENT

Nanoscale Engineering Of Magnetism

The control of magnetism is important in the operation of many modern electronic devices. Hard disks, still the prevalent device for storage of large amounts of data, store information by encoding it in magnetic units. Providing new means to control and manipulate magnetism, therefore, provides new ways to read, write, or process information.

A material class that exhibits intricate magnetic properties are strongly correlated electronic materials. These materials have complicated magnetic ground states which, in many cases, are energetically in close proximity. These materials are therefore prime candidates for use in future devices as they can be tuned between different magnetic states by varying certain control parameters such as external magnetic field or through slight distortions of the crystal structure of the material. Another parameter that can be used to change the magnetic order of a material on the nanoscale is through dopant atoms. Regions of the material with higher or lower numbers of dopant atoms can, therefore, exhibit startlingly different magnetic structures.

ADVERTISEMENT

One such material is iron telluride (Fe1+xTe), a strongly correlated magnetic material that exhibits different magnetic ground states depending on the amount of excess iron in the sample. Various theories have been put forward to explain how the magnetic structure in this material is stabilized, and what the role of the extra iron atoms is. Is it these extra iron atoms which control the magnetic ground state, or rather the crystal structure that changes with the addition of excess iron, or rather a combination of the two? To experimentally answer this question, we have used spin-polarised scanning tunneling microscopy in vector magnetic fields to map out in three dimensions the surface magnetic structure of Fe1+xTe at increasing Fe dopant concentration.

Credit: Christopher Trainer

Scanning tunneling microscopy (STM) uses a sharp, metallic tip to provide atomically resolved imaging on sample surfaces. With a magnetic probe tip (which can be thought of as having a tiny bar magnet attached to the tip apex), one can also use STM to determine the surface magnetic structure that would remain invisible to a non-magnetic tip. Our STM is mounted in a unique “Vectormagnet” system that allows for the application of high magnetic fields in any direction relative to the Iron telluride sample. The ability of the tip to detect the magnetism of the sample depends on the relative orientation of the tip and sample’s “magnetic poles,” therefore, by changing the direction of the magnetic field that we apply to the tip we can determine precisely how the atomic scale “magnetic poles” of the sample are aligned in space. Using this setup, we have successfully mapped out the surface magnetic structure of Fe1+xTe and how it changes with increasing excess iron concentration, x.

We furthermore could show that not only can we map out the magnetic structure in all three spatial dimensions, but moreover use the tip of the STM to manipulate the surface magnetic structure. To demonstrate this, we have first checked that the surface magnetic order that we observe is consistent with the known spiral-type magnetic structure of Fe1+xTe samples. After removing iron atoms from the surface by collecting them with the tip, the samples exhibit a new checker-board magnetic order. As the underlying crystal structure is unaffected before and after the iron is removed, this demonstrates how the magnetic order of the sample can be manipulated through controlling the surface excess Fe concentration and by distorting the crystal structure.

Our results highlight a new way towards using local atomic doping and changes in the crystal structure to control the magnetism in Iron telluride and related compounds at the nanoscale. We expect that our methodology to engineer and control magnetic order at the nanoscale will be useful for the development of future devices that rely on controlling and manipulating magnetism.

ADVERTISEMENT

These findings are described in detail in the article entitled Manipulating surface magnetic order in iron telluride, which has been recently published free to view in the online journal Science Advances.

Comments

READ THIS NEXT

CD4 T Cells And Brain Degeneration In Aging Adults

As living standards increase and health provisions become better and more accessible to all, we can look forward to living longer. […]

Ultrasmall Nanoplatelets: The Ultimate Tuning Of Optoelectronic Properties

 Semiconductor nanocrystals with unique optoelectronic properties have emerged as promising materials for applications in solar technologies, including solar cells, solar-driven […]

Tuning The State-Of-The-Art Numerical Simulator To Recover Energy From Methane Hydrates

With the ever-increasing demand for cleaner energy, natural gas is playing a growing role in the global energy mix replacing […]

The Driving Forces Of Grain Growth And Densification During Sintering Evolution

Manufactured ceramics are one of the first technological achievements of humankind, and after thousands of years, although their spectrum of […]

Gates Foundation Backs Plan To Combat Malaria By Bio-Engineering Mosquitoes

Mosquitoes are one of the primary ways that malaria spreads across the globe, and mosquitoes are also responsible for killing […]

The Power Of “Coping” In Diabetes Self-Management: Why Providers Should Care About Their Patient’s Ability To “Cope”

Over 29 million people in the US are estimated to have diabetes, with projections that number will increase to 642 […]

Octlantis: The Newly Discovered Octopus City

Recently scientists have discovered a bustling community of approximately 15 gloomy octopi, also known as the Common Sydney Octopus, and […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?