Nanocrystals Give Hematite Rainbow Colors

Naturally iridescent materials such as opal or a butterfly’s wing have long fascinated onlookers for their ability to produce spectacular rainbow colors. Now, researchers have uncovered the cause of the vibrant display in another naturally iridescent material, the iron oxide mineral known as rainbow hematite. Pennsylvania State University geochemist Peter J. Heaney and his student Xiayang Lin used a variety of imaging and spectroscopy techniques to investigate the chemical makeup and surface structure of a rainbow hematite sample from Brazil (Gems & Gemol. 2018, DOI: 10.5741/GEMS.54.1.28). They found that the mineral contains stacked sheets of spindle-shaped nanocrystals that are arranged at 120-degree angles.

The nanocrystal array acts as a diffraction grating, splitting and scattering beams of light to produce the rainbow effect. The researchers also calculated a chemical formula (Fe_1.81Al_0.23P_0.03O₃) for the mineral, which contains aluminum and phosphorus impurities in addition to its major iron and oxygen components. The presence of those impurities within the crystal structure may have prompted the nanoparticles to grow into spindle shapes rather than into more symmetrical rhombohedrons, Heaney says. He thinks the findings could inspire new nanocrystal-based iridescent coatings.

Scientists Discover New Magnetic Element

A new experimental discovery, led by researchers at the University of Minnesota, demonstrates that the chemical element ruthenium (Ru) is the fourth single element to have unique magnetic properties at room temperature. The discovery could be used to improve sensors, devices in the computer memory and logic industry, or other devices using magnetic materials.  

The use of ferromagnetism, or the basic mechanism by which certain materials (such as iron) form permanent magnets or are attracted to magnets, reaches back as far as ancient times when lodestone was used for navigation. Since then only three elements on the periodic table have been found to be ferromagnetic at room temperature—iron (Fe), cobalt (Co), and nickel (Ni). The rare earth element gadolinium (Gd) nearly misses by only 8 degrees Celsius.

Magnetic materials are very important in industry and modern technology and have been used for fundamental studies and in many everyday applications such as sensors, electric motors, generators, hard disk media, and most recently spintronic memories.

As thin film growth has improved over the past few decades, so has the ability to control the structure of crystal lattices—or even force structures that are impossible in nature. This new study demonstrates that Ru can be the fourth single element ferromagnetic material by using ultra-thin films to force the ferromagnetic phase.

The details of their work are published in the most recent issue of Nature Communications. The lead author of the paper is a recent University of Minnesota Ph.D. graduate Patrick Quarterman, who is a National Research Council (NRC) postdoctoral fellow at the National Institute of Standards and Technology (NIST).

“Magnetism is always amazing. It proves itself again. We are excited and grateful to be the first group to experimentally demonstrate and add the fourth ferromagnetic element at room temperature to the periodic table,” said University of Minnesota Robert F. Hartmann professor of electrical and computer engineering Jian-Ping Wang, the corresponding author for the paper and Quarterman’s advisor.

“This is an exciting but hard problem. It took us about two years to find a right way to grow this material and validate it. This work will trigger the magnetic research community to look into fundamental aspects of magnetism for many well-known elements,” Wang added.

Helium Ion Microscopy Reveals Mysteries of Iron-Oxide Covered Bacteria

Some iron-oxidizing bacteria make organic-mineral filaments that extend from their surfaces. But how they are formed remains a puzzle. Now, using helium ion microscopy (HIM), James M. Byrne of the University of Tübingen and his colleagues have captured these stalks forming in unprecedented detail (Environ. Sci. Technol. Lett. 2018, DOI: 10.1021/acs.estlett.8b00077). Previous imaging efforts used scanning electron microscopy, but this technique has inferior resolution and in this context requires coatings that distort the structures being studied.

The group cultured bacteria isolated from low-oxygen sediments in a Denmark bay and analyzed the samples with HIM over a month to document how the structures changed. First, spiral-shaped stalks formed. Eventually, mineral crystals coated the spirals so heavily that their shapes were no longer discernible. “It really blew my mind when we started to see these objects forming,” Byrne says. The spirals were mostly organic, whereas the mineral deposits were lepidocrocite, an iron oxide-hydroxide mineral, elemental analysis showed. Some researchers think the structures sequester toxic, dissolved iron(II) in the environment as insoluble iron(III), protecting the microbes. More work may solve that mystery, too.

Magnetic Quiz - We Have Two Winners

In preparation of our 2018 Magnetic Carrier Meeting, Vitalii Zablotskii made up a small quiz about magnetism. It was not easy, and nobody could answer all the questions correctly. But we had two conference participants who got the same high score. As a thank you, they received a magnetic knife holder - something really useful for your kitchen.

If you have not answered the quiz questions yet, you might give it a try  with the the questions here. And if you think you got it all right, check to see Vitalii's answers here. Did you get it all correctly?

Thank you very much Vitalii for preparing this for us! And by the way, there will be another quiz coming up in the near future. Keep posted.

Big Honor for Maxim Nikitin

Russia's President Vladimir Putin presented our own physicist/mathematician Maxim Nikitin of Moscow Institute of Physics and Technology (MFTI) on February 8, 2018 with an award to young researchers and scientists at the House of Scientists (Scientists' Club) of the Siberian Branch of the Russian Academy of Sciences. Well deserved Maxim!

Hear of Magnetic Surgery, Anybody?

In recent years, magnetic compression anastomosis (MCA) developed quickly. Many breakthroughs and innovations were made in the magnetic anchoring technology (MCT) and magnetic navigation technology (MNT). The development of these technologies started a new research field of magnetic surgery. However, many key problems have not been solved yet. For this reason, Xi'an Jiaotong University under the guidance of president Yi Lv is organizing the 1st International Congress of Magnetic Surgery (ICMS-2018) ,which will be held from June 1-3, 2018 in Xi'an, China.

It does not seem that the people in this group use magnetic particles yet, but who knows what the future brings! Check out the program at http://icms.medmeeting.org/Content/92865.

Magnetic Carrier Meeting 2018 in Copenhagen

Our 12th International Conference on the Scientific and Clinical Applications of Magnetic Carriers took place at the University of Copenhagen's new Maersk building.from May 22-26, 2018. Most of the 328 participants are visible from the picture below - click on it to get a higher resolution version.

If you want to check out the program, the entire abstract booklet is available online.

Weird Magnetic Effect Could Improve Computer Memory

For decades, applied physicists and semiconductor companies have developed computer memory that uses the direction of a magnetic field to store data. A magnetic pulse or a jolt of electricity can change the properties of an island of magnetic material, flipping its field up or down to represent a 1 or a 0. The primary advantage of this so-called magnetoresistive random access memory (MRAM) is its durability. Johns Hopkins University physicist Chia-Ling Chien developed memory that can be written using smaller pulses of current. This would reduce power requirements and improve the lifetime of the memory arrays. Chien worked with an experimental device made up of nanometer-thin layers of a cobalt-iron-boron ferromagnet, a metal oxide, and tungsten held between a pair of gold electrodes. The researchers could flip the polarization of the CoFeB magnet by applying current through the electrodes, but only in the presence of a magnetic field. The tungsten layer acts as a kind of electron filter, allowing in only electrons with a particular spin. The momentum of that spin gets transferred to the magnet and flips the field.

While studying this device, Chien’s team found something weird. They wanted to see what happened when they broke one of the memory devices. They added a layer of platinum under the tungsten, expecting it would cancel out the spin-switching effect. “Anyone who understands spin-orbit torque will realize this is a stupid thing to do, because tungsten and platinum have opposite spin currents.” But the device didn’t stop working. Instead, the team found they could switch the platinum-frosted device simply by applying an electrical current—no magnetic field required. This simplification means such devices should be less complicated to build and operate. For more info, see here.