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Spinel structure high entropy oxide (CrMnFeCoNi)3O4

Neutrons Clarify Convoluted Magnetic Materials

CINS Scattering Spotlight: Graham Johnstone

Source: Mitchell DiPasquale
Contact: webmaster@cins.ca
Image: Spinel structure high entropy oxide (CrMnFeCoNi)3O4.

Everyone is waiting for the next big technological leap. As devices grow in complexity, the limits of materials and hardware are pushed toward their energetic and physical limits. Materials researchers across the globe redesign and tweak hardware to extend capabilities, but before too long these roadblocks will be unavoidable.

A technological revolution demands revolutionary hardware, and a new class of materials called high entropy oxides (HEOs) may have the necessary exotic electromagnetic properties to reinvigorate the field.

Graham Johnstone

Graham Johnstone, Stewart Blusson Quantum Matter Institute, University of British Columbia

HEOs are crystalline materials with ordered oxygen and a mixture of randomly positioned metal ions. These unique materials possess intrinsic chemical disorder, lending fascinating properties that hold potential to develop technologies from reversible batteries to multiferroic components to make devices more efficient.

Graham Johnstone, a graduate student with Dr. Alannah Hallas at the Stewart Blusson Quantum Matter Institute of the University of British Columbia, is studying HEOs to define relationships between magnetism and chemical disorder.

High Entropy Oxide materials provide us with a wellspring of elemental combinations through which we can explore the relationship between magnetism and intense chemical disorder.

Graham Johnstone, Stewart Blusson Quantum Matter Institute, University of British Columbia

Graham is using a spinel structure HEO with the composition (CrMnFeCoNi)3O4 to dig deeper into these complex magnetic behaviours. In bulk, this HEO material remarkably retains its ferrimagnetic properties above room temperature. Theory predicts intrinsically disordered crystals that are doped with non-magnetic metals to exhibit decreased magnetism; however, HEOs have proven to be a stark exception to the rule.

To further define the origins of this magnetic paradox, Graham will use neutron diffraction to probe the magnetic properties of the various crystallographic sites in the spinel structure HEO. Neutrons are uncharged and possess the property of spin, offering an essential tool to probe the arrangement of magnetic moments deep inside materials at the sublattice scale – a feat not accomplished by other techniques.

In addition to shedding light on the nature of HEO magnetism, neutrons will also help Graham distinguish the cause of thermal changes in magnetic susceptibility to further explain the complex and remarkable magnetic properties of HEOs.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you share your research stories by contacting drew.marquardt@uwindsor.ca.

Serpintinite - Simone Pujatti

Neutrons Take Geology to New Scales

CINS Scattering Spotlight: Simone Pujatti

Source: Mitchell DiPasquale 
Contact: webmaster@cins.ca
Image: (Left) Serpentinite Rock (Right) 3D Rendering of porous network in a serpentinite (scale = 500 nm).

We’re all familiar with how rainwater flows across the ground into streams and rivers after a heavy rainfall. But what happens to the water that soaks deep into the soil and rocks?

The reactions between water and rock control the chemical evolution of the Earth. Water seeping through the Earth’s crust changes the rock and influences global-scale processes such as plate tectonics. One of the most important of these reactions is serpentinization, which occurs when rocks from the Earth’s mantle, upwelling at mid-ocean ridge, interact with seawater. The resulting green and scaly serpentinites may have been the key to the origin of life.

Simone Pujatti, University of Calgary
PhD Student, Simone Pujatti, University of Calgary

Vast regions of oceanic mantle rock have almost completely been transformed into serpentinite, releasing hydrogen and methane that can be used as nutrients by early-Earth microorganisms. The process of how water has been able to infiltrate deep into these highly impermeable rocks is still very much a mystery.

Conceptually, serpentinization deep into the mantle rock is fueled by a constant supply of water and solutes that creep through the porous network formed by the spaces between the solid particles of rock. In reality, theory predicts that the serpentinite formed in the reaction should clog the pores of the rock, sealing off the supply of reactants, and stopping the transformation. Unfortunately, to limitations of classic geological characterization techniques, researchers have yet to study the extremely small pore structure of serpentinites – ranging from tens to hundreds of nanometers.

Simone Pujatti, a PhD student at the University of Calgary, is employing a modern solution to research the feedbacks between serpentinization and porosity to explain how this reaction has taken over the Earth’s mantle.

Using a combination of small and ultra-small angle neutron scattering, Simone will capture and quantify the whole distribution of pore sizes in various mantle rocks drilled from under the Atlantic Ocean. Each sample is meticulously chosen to reveal the evolution of the pore network as serpentinization progresses.

“The evidence generated will elucidate the relationship between serpentinization extent, volume increase and changes in porosity. This will impact our understanding of systems both at the molecular level, as the pores can be inhabited by microorganisms, and at the regional scale since porosity changes drive serpentinization reactions through the oceanic crust.”

Simone Pujatti, University of Calgary

Neutrons provide a non-destructive technique to study the nano-scale porosity of materials, including rocks, under the high temperatures and pressures in which they naturally form. The broad microstructural range quantifiable by combining multiple neutron scattering techniques offers a unique tool to modern geoscientists, and Simone hopes it will provide the evidence necessary to resolve a century-old issue about solid volume increase during serpentinization.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you to share your research stories by contacting tharroun@brocku.ca

Nickel hydride catalyst

Neutrons Uncover Clues for Better Catalysts

CINS Scattering Spotlight: Dr. Manar Shoshani

Source: Mitchell DiPasquale 
Contact: webmaster@cins.ca
Image: A) 1.5 mm3 single crystalline nickel-hydride for neutron diffraction. B) Neutron diffraction-solved structure. C) ChemDraw depiction of cluster.

From cleaning the toxic exhausts of your car’s engine, to the green promise of plastic upcycling, to the biological processes that keep you alive – achieving efficient results in chemical changes is driven by catalysts.

The ability of nature to selectively carry out multi-electron chemistry under ambient conditions has long inspired catalytic design.  Innovation in synthetic catalysts can unlock novel reactions and allow cheaper, cleaner, and more efficient pathways to new and improved materials.

Dr. Manar Shoshani
Dr. Manar Shoshani

Former UWindsor PhD student Manar Shoshani took inspiration from multi-metallic enzyme active sites to try to emulate this robust reactivity in homogenous transition metal clusters. Under the guidance of Dr. Samuel A. Johnson, Manar sought to understand how the multi-metal centres interact to promote catalysis, with hopes of providing a trajectory toward intelligent design of better catalysts. 

With molecular nickel-hydride clusters, Manar observed remarkable activations of C–C, C–O, and C–S bonds as well as catalytic activation of C–H bonds, all of which proceeded rapidly at room temperature. Knowledge on the solid-state structure of the complex is vital to decipher the mechanistic intricacies that drive these processes.

“Determining the unambiguous solid-state structure of these complexes is imperative to understanding both the properties of the cluster, as well as the potential for these clusters to serve as catalysts.”

– Dr. Manar Shoshani, Caltech Post-Doctoral Fellow

Synthetic chemists naturally lean on X-ray crystallography for structural information; however, light atoms (particularly hydrogen), coordinated in these complexes are largely invisible to studies by X-ray. For Manar, neutron diffraction served as the ideal complement to be able to pinpoint the hydride locations in the cluster, and to clue into the details of metal-metal cooperativity.

A step further, as neutrons interact with hydrogen and deuterium differently, the experiment also provided insight into the catalytic hydrogen-deuterium exchange activity of the clusters. Neutrons offer an exceptional means to uncover the finesse of transition metal hydride catalysts. A deeper understanding of metal-metal cooperativity can help usher in a new wave of efficiency with rationally designed catalysts.

After completing his PhD, Dr. Shoshani continues to contribute to catalyst innovation as a post-doctoral fellow at the California Institute of Technology.

For more information on this work, the published manuscript can be found at Shoshani, Manar M., Robert Beck, Xiaoping Wang, Matthew J. McLaughlin, and Samuel A. Johnson. Inorganic Chemistry 57, 5 (2017): 2438-2446.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you to share your research stories by contacting tharroun@brocku.ca

Atomic structure of a mineral perovskite

Neutrons Point to Next-Generation Computer Memory Materials

CINS Scattering Spotlight: Dr Dalini Maharaj, TRIUMF

Source: Mitchell DiPasquale 
Contact: webmaster@cins.ca
Image: Crystal structure of a mineral perovskite. (Wikimedia CC-BY-SA 3.0)

As our music and movie libraries grow and the number of apps we use multiplies, everyone wants faster devices with larger data storage. Former McMaster PhD student Dalini Maharaj studies novel magnetic materials that could very well usher in the next generation data storage technology, particularly in disk drive read-and-write heads. In principle, one could reduce the size of the data storage unit if the data density could be increased in these hard-disks. New kinds of quantum materials are needed to fulfil this promise.

“Of course, before these new technologies can be realized, much work needs to be performed to understand the properties of the candidate materials.” – Dr. Dalini Maharaj, TRIUMF Post-Doctoral Fellow

Dr. Maharaj’s PhD work involved the study of the quantum magnetic properties of crystalline materials via X-ray and neutron scattering methods. Working in Prof. Bruce D. Gaulin’s group at McMaster University, she synthesized novel materials which are theoretically predicted to exhibit exotic magnetic properties. This class of materials, referred to as the double perovskites, have phases that involve `frustrated` magnetic interactions, whereby the magnetic dipoles of the atoms cannot arrange themselves into a low energy configurations. Members of this family are widely studied as they are shown to exhibit a wide variety of unique properties including superconductivity, ferroelectricity and colossal magnetoresistance, the latter being a prime candidate for increasing the data density of hard drives. In particular, Dalini’s doctoral work involved the study of non-trivial arrangements of magnetic atoms in d-electron double perovskites which are driven by magnetic interactions that can only be theoretically analysed with advanced quantum mechanics.

Dr. Dalini Maharaj

Neutrons are an indispensable probe of the magnetic properties of materials as they are electrically neutral and they possess the property of spin. These properties enable neutrons to deeply penetrate matter and interact directly with the magnetic degrees of freedom in solid state materials. The energy spectra which are obtained from neutron scattering experiments provide important clues for identifying the magnetic ground state of the materials being investigated.

Most recently, Dalini’s neutron scattering studies on the cubic double perovskite materials led to discover the first instance of octupolar order in d-electron magnets. This discovery highlights the relevance of multipolar interactions in heavy d-electron magnets and consequently, the potential for the realization of novel materials for future applications.

Upon completing her PhD, Dalini remained in the field of neutron sciences and is currently completing a postdoctoral fellowship at TRIUMF, through the University of Windsor, studying potential targets and moderators for a future compact accelerator neutron source.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you to share your research stories by contacting tharroun@brocku.ca

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The Canadian energy sector has developed standard practices to ensure that oil and gas pipelines remain safe as they age. For the past decade, these standard practices have been influenced by a team of researchers, including one University of Alberta professor and his industrial partners, who use neutron beams to better understand stress and corrosion in pipeline steel. Continue reading Ensuring oil and gas pipeline integrity using neutron beams →

Neutrons assist in the development of sustainable electricity grids

With sponsorship from Tesla Motors, one ‘Gold medal’ Canadian scientist is using neutron beams in the quest to reduce the cost of energy storage technologies, which is vital for the widespread adoption of renewable energy sources and electric vehicles.

Continue reading Neutrons assist in the development of sustainable electricity grids →