Study reveals two huge hot blobs of rock influence Earth’s magnetic field

University of Liverpool

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Exploring Earth’s deep interior is a far bigger challenge than exploring the solar system. While we have travelled 25 billion km into space, the deepest we have ever gone below our feet is just over 12 km.

Consequently, little is known about the conditions at the base of the mantle and the top of the core – the most significant interface in the Earth’s interior and the region where new research has now uncovered exciting magnetic activity.

In a study published in Nature Geoscience, research led by the University of Liverpool has identified magnetic evidence that two immense, ultra-hot rock structures located at the base of Earth’s mantle, around 2,900 kilometres beneath Africa and the Pacific, affect the underlying liquid outer core.

The study shows that these enormous blobs of solid, superheated material — encircled by a pole-to-pole ring of cooler rock — have been shaping Earth’s magnetic field for millions of years.

Both measuring ancient magnetic fields and simulating the processes that generate them are technically demanding.

To investigate these deep-Earth features, the research team combined palaeomagnetic observations with advanced computer simulations of the geodynamo - the flow of liquid iron in the outer core that generates Earth’s magnetic field like a wind-turbine generates electricity.

Numerical models enabled them to reconstruct key observations of the behaviour of the magnetic field seen over the past 265 million years. Even with a supercomputer, running such simulations, especially over long timescales, represents an immense computational challenge.

The results revealed that the outer core’s upper boundary is far from uniform in temperature. Instead, it displays strong thermal contrasts, with localised hot regions capped by the continent-sized rock structures.

It also showed that some parts of the magnetic field appear to have remained relatively stable for hundreds of millions of years, while others have changed significantly through time.

Andy Biggin, Professor of Geomagnetism at the University of Liverpool, said: “These findings suggest that there are strong temperature contrasts in the rocky mantle just above the core and that, beneath the hotter regions, the liquid iron in the core may stagnate rather than participate in the vigorous flow seen beneath the cooler regions.

“Gaining such insights into the deep Earth on very long timescales strengthens the case for using records of the ancient magnetic field to understand both the dynamic evolution of the deep Earth and its more stable properties.

“These findings also have important implications for questions surrounding ancient continental configurations—such as the formation and breakup of Pangaea—and may help resolve long-standing uncertainties in ancient climate, palaeobiology, and the formation of natural resources. These areas have assumed that Earth’s magnetic field, when averaged over long periods, behaved as a perfect bar magnet aligned with the planet’s rotational axis. Our findings are that this may not quite be true”

The paper, ‘Mantle heterogeneity influenced Earth’s ancient magnetic field’ is published in Nature Geosciences (DOI: 10.1038/s41561-025-01910-1)

The study was conducted by scientists from the DEEP (Determining Earth Evolution using Palaeomagnetism) research group in the University of Liverpool’s School of Environmental Sciences working alongside researchers from the University of Leeds.

Professor Biggin and his team specialise in analysing the magnetic signatures preserved in rocks from around the world to reconstruct the history of Earth’s magnetic field and internal dynamics.

DEEP was established in 2017 with support from the Leverhulme Trust and the Natural Environment Research Council (NERC).

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Journal

Nature Geoscience

DOI

10.1038/s41561-025-01910-1 

Article Publication Date

3-Feb-2026

 

Oxygen-modified graphene filters boost natural gas purification

Adding oxygen to ultrathin graphene enables efficient carbon dioxide removal from methane while maintaining high permeability

Chiba University

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Introducing oxygen groups at graphene pore edges strengthens carbon dioxide (CO2) selectivity over methane (CH4), allowing rapid gas flow while efficiently removing impurities from gas mixtures.

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Credit: Associate Professor Tomonori Ohba from Chiba University, Japan

As we shift toward more sustainable fuels, natural gas and biogas, which mainly contain methane (CH4), have become important sources of energy and raw materials for chemical production. However, these gases also contain impurities that must be removed before use. One major contaminant is carbon dioxide (CO2), which reduces the energy content of the gas and can cause corrosion in pipelines.

One promising method for efficiently separating CO2 from these gases is filtration using graphene membranes containing nanosized pores. Graphene is particularly attractive as a filtration material because of its exceptional mechanical strength and chemical and thermal stability. While pristine graphene is naturally impermeable to gases, introducing pores allows it to selectively separate gas molecules.

Now, researchers at Chiba University, Japan, led by Associate Professor Tomonori Ohba, along with Shunsuke Hasumi from the Graduate School of Science, Chiba University, have shown how ultrathin oxygen-functionalized graphene membranes can efficiently separate CO2 from CH4. Their study was made available online on December 8, 2025, and will be published in Volume 248 of the journal Carbon on February 5, 2026. The findings offer a potential pathway toward next-generation gas purification systems.

“Membrane separation has emerged as a promising and environmentally friendly technique that provides high selectivity and permeability. Graphene could be an extremely permeable gas separation membrane; however, its practical implementation and separation ability require further improvement,” says Assoc. Prof. Ohba.

The pore size of the graphene membrane was found to be critical for effective gas separation. If the pores are too large, both CO2 and CH4 pass through indiscriminately. To investigate this effect, the researchers measured the flow of CO2 and CH4 through graphene membranes mounted in a custom-built mass spectrometer system. Alongside these experiments, they conducted detailed computer simulations that tracked the movement of CO2 and CH4 molecules through graphene pores ranging from 0.21 to 0.99 nanometers. These calculations accounted for molecular interactions and long-range Coulomb interactions, allowing the team to systematically examine how pore diameter and surface chemistry influence gas permeation.

The simulation results showed that porous graphene membranes exhibit extremely high permeability, allowing gases to pass through very easily. However, when pore sizes exceeded about 0.5 nanometers, the membranes showed little ability to distinguish between CO2 and CH4. Only pores closer to 0.4 nanometers exhibited noticeable selectivity. Experimental tests confirmed this overall trend, although the measured CO2 permeability was lower than predicted by simulations because the experimental membranes consisted of multiple graphene layers instead of a single layer.

A key factor explaining the difference between simulations and experiments was the presence of oxygen functional groups on real graphene membranes. These oxygen-containing groups naturally form at defects and edges in graphene. When the researchers incorporated these oxygen-modified regions into their simulations, the membrane allowed CO2 to pass through more easily while also separating it more effectively from CH4.

To confirm this experimentally, the researchers treated graphene membranes with oxygen plasma, intentionally introducing oxygen functional groups. The modified membranes showed significantly improved separation performance, closely matching the simulation results.

The enhanced selectivity was attributed to stronger interactions between CO2 molecules and oxygen functional groups at the edges of graphene pores. CO2 is more strongly attracted to these oxygen sites than CH4, allowing it to pass through the membrane more readily, even when pore sizes are relatively large.

The findings demonstrate that graphene membranes can achieve improved CO2 and CH4 separation while maintaining high permeability and flow rates, opening the door to industrial applications. “Such technology could lead to cheaper and cleaner energy by making biogas and natural gas purification more efficient, lowering CO2 emissions through high-efficiency separation, and reducing the energy required for industrial gas processing,” says Assoc. Prof. Ohba.

To see more news from Chiba University, click here.

 

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Reference:
Authors: Shunsuke Hasumi and Tomonori Ohba
Affiliations: Graduate School of Science, Chiba University, Japan
DOI: 10.1016/j.carbon.2025.121147

 

About Associate Professor Tomonori Ohba from Chiba University, Japan
Tomonori Ohba is an Associate Professor and Director of the Ohba Research Group at the Department of Chemistry, Graduate School of Science, Chiba University, Japan. He primarily works in the field of physical chemistry, aiming to elucidate chemical phenomena at the nanomolecular level by employing advanced theoretical and experimental methods. He also explores nanospaces to control molecular motion, investigate molecular behavior, and discover new molecular reactivities. His extensive research work, published in numerous reputable journals, has been cited more than 5,000 times.

 

Funding:
This research was supported by JSPS KAKENHI (Grant Number: 23H01999).

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Journal

Carbon

DOI

10.1016/j.carbon.2025.121147 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Enhancing the CO2/CH4 gas separation performance of graphene membranes via oxygen functionalization

Article Publication Date

5-Feb-2026

 

A new thermoelectric material to convert waste heat to electricity

Researchers discover a new candidate, the mixed-semimetal MoSi2, that can be used to develop efficient thermoelectric devices

Tokyo University of Science

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MoSi2 demonstrates clear and large transverse thermopower, establishing itself as a promising candidate for developing efficient transverse thermoelectric devices.

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Credit: Associate Professor Ryuji Okazaki from Tokyo University of Science, Japan. https://www.nature.com/articles/s43246-025-01050-4

Thermoelectric conversion devices offer a promising route for sustainable heat-to-energy conversion. They are particularly attractive for recovering energy from waste heat, such as that produced by conventional fossil fuel-based engines, improving their overall energy efficiency. Around 20–50% of the input energy is lost as waste heat in industries. This could be used as source by thermoelectric conversion devices. These devices also have the potential to enable portable power generation, for example, to run small sensors in remote locations.

Currently, most thermoelectric devices rely on the longitudinal thermoelectric effect in which electricity is generated in the same direction as heat flow. Such devices generally consist of alternating layers of p- and n-type semiconductors connected in series. p- and n-type semiconductors generate electricity in opposite directions. When a temperature difference is applied across the device, the charge carriers in these materials move from the hot side to the cold side, generating a voltage. However, stacking many layers increases the electrical contact resistance at their interfaces, which leads to energy losses and limits overall efficiency.

Transverse thermoelectric (TTE) devices that generate voltage perpendicular to the direction of heat flow are a promising alternative. Importantly, TTE devices can be made from a single material, eliminating the need for multiple interfaces, significantly reducing contact resistance and improving overall efficiency. This also makes manufacturing simpler. However, materials that exhibit a strong TTE effect are rare.

In a recent study, a research team led by Associate Professor Ryuji Okazaki from the Department of Physics and Astronomy at Tokyo University of Science (TUS), Japan, demonstrated TTE behavior in the mixed-dimensional semimetal molybdenum disilicide (MoSi2). The team also included Ms. Hikari Manako, Mr. Shoya Ohsumi, and Assistant Professor Shogo Yoshida from TUS, as well as Assistant Professor Yoshiki J. Sato from Saitama University, Japan. Their findings were published in the journal Communications Materials on December 29, 2025.

“We wanted to explore new transverse thermoelectric materials. Recently, the presence of axis-dependent conduction polarity (ADCP) in a material has been recognized as an indicator for TTE generation ability,” explains Dr. Okazaki. “Mixed-metal conductors like MoSi2 are potential ADCP candidates, but their thermopower generation ability has not been thoroughly investigated.”

The researchers measured the transport properties of MoSi2 using both experiments and first-principles calculations. Specifically, they examined temperature dependence of resistivity and thermal conductivity, as well as longitudinal thermopower, along the material’s two crystallographic axes. Thermopower measurements demonstrated clear ADCP, which was further confirmed through Hall resistivity measurements.

To probe the origin of ADCP, the researchers examined the electronic structure of MoSi2 using first-principles calculations. They found that ADCP originates from a mixed-dimensional Fermi surface structure, consisting of two Fermi surfaces with opposite polarities. The Fermi surface is essentially a boundary that separates filled and empty electronic states of a solid material. The shape of this surface, therefore, strongly determines the electronic and transport properties of the material.

Next, the researchers directly measured transverse thermopower of MoSi2 by applying a temperature difference at a 45-degree angle to one of its crystallographic axes. The results showed clear and substantial transverse thermopower signal. Notably, the magnitude of this signal was larger than that observed for tungsten disilicide (WSi2), another ADCP material examined previously by the team, mainly due to differences in how its electrons are distributed. Moreover, the transverse thermopower of MoSi2 was comparable to that of anomalous Nernst materials, which are magnetic materials well known for their strong TTE effects.

“These findings establish MoSi2 as an ideal material for TTE applications, particularly in the low-temperature range, thereby expanding the list of viable candidates,” remarks Dr. Okazaki. “Moreover, both MoSi2 and WSi2 show that mixed-dimensional Fermi surfaces are important for the emergence of ADCP and therefore transverse thermopower.”

By utilizing thin film of MoSi2 as an ideal material for TTE applications, large heat source area could be covered to produce voltage. Overall, this study represents a new direction for finding TTE materials, paving the way for efficient waste heat recovery systems for a greener future.

 

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Reference
DOI: 10.1038/s43246-025-01050-4  

About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

About Associate Professor Ryuji Okazaki from Tokyo University of Science
Dr. Ryuji Okazaki is currently an Associate Professor at the Department of Physics and Astronomy at Tokyo University of Science, Japan. He received his Ph.D. degree from Kyoto University, Japan. He has published over 150 articles that have received over 3,300 citations, including a feature article in the journal Applied Physics Letters. He is the recipient of the Papers of Editors' Choice by JPSJ in 2017 from The Physical Society of Japan and the 2012 Award for Encouragement of Research in Materials Science. His research is focused on correlated electron systems and condensed matter physics.

Laboratory website 
Official TUS website 

 

Funding information
This work was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI via Grants No. 22K20360, No. 22H01166, and No. 24K06945, and the Research Foundation for the Electrotechnology of Chubu (REFEC) via Grant No. R-04102.

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Journal

Communications Materials

DOI

10.1038/s43246-025-01050-4 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Axis-Dependent Conduction Polarity and Transverse Thermoelectric Conversion in the Mixed-dimensional Semimetal MoSi2