Magnetic cooling – using a frustrated desert mineral

Research team identifies atacamite as a magnetocaloric material

Helmholtz-Zentrum Dresden-Rossendorf

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Artistic representation of the magnetic sawtooth structure of atacamite: The magnetic moments (green) of the Cu ions (white and blue) cannot be completely aligned antiparallel to each other due to the triangular arrangement. At low temperatures, this results in the compromise arrangement shown. An external magnetic field destroys it and leads to an unexpectedly strong magnetocaloric effect, which could be used for efficient cooling.

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Credit: B. Schröder/HZDR

Natural crystals fascinate with their vibrant colors, their nearly flawless appearance and their manifold symmetrical forms. But researchers are interested in them for quite different reasons: among the countless minerals already known, they always discover some materials with unusual magnetic properties. One of these is atacamite, which exhibits magnetocaloric behavior at low temperatures – that is, the material’s temperature changes significantly when it is subjected to a magnetic field. A team headed by TU Braunschweig and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now investigated this rare property (DOI: 10.1103/PhysRevLett.134.216701). In the long term, the results could help to develop new materials for energy-efficient magnetic cooling.

The emerald-green mineral atacamite, named for the place it was first found, the Atacama Desert in Chile, gets its characteristic coloring from the copper ions it contains. These ions also determine the material’s magnetic properties: they each have an unpaired electron whose spin gives the ion a magnetic moment – comparable to a tiny needle on a compass. “The distinct feature of atacamite is the arrangement of the copper ions,” explains Dr. Leonie Heinze of Jülich Centre for Neutron Science (JCNS). “They form long chains of small, linked triangles known as sawtooth chains.” This geometric structure has consequences: although the copper ions’ spins always want to align themselves antiparallel to one another, the triangular arrangement makes this geometrically impossible to achieve completely. “We refer to this as magnetic frustration,” continues Heinze. As result of this frustration, the spins in atacamite only arrange themselves at very low temperatures – under 9 Kelvin (−264°C) – in a static alternating structure.

When the researchers examined atacamite under the extremely high magnetic fields at HZDR’s High Magnetic Field Laboratory (HLD), something surprising emerged: the material exhibited a noticeable cooling in the pulsed magnetic fields – and not just a slight one, but a drop to almost half of the original temperature. This unusually strong cooling effect particularly fascinated the researchers, as the behavior of magnetically frustrated materials in this context has scarcely been studied. However, magnetocaloric materials are considered a promising alternative to conventional cooling technologies, for example for energy-efficient cooling or the liquefaction of gases. This is because, instead of compressing and expanding a coolant – a process that takes place in every refrigerator – they can be used to change the temperature by applying a magnetic field in an environmentally friendly and potentially low-loss approach.

What is the origin of this strong magnetocaloric effect?

Additional studies at various labs of the European Magnetic Field Laboratory (EMFL) provided more in-depth insights. “By using magnetic resonance spectroscopy, we were clearly able to demonstrate that the magnetic order of atacamite is destroyed when a magnetic field is applied,” explains Dr. Tommy Kotte, a scientist at HLD. “This is unusual as the magnetic fields in many magnetically frustrated materials usually counteract the frustration and even encourage ordered magnetic states.”

The team found the explanation for the mineral’s unexpected behavior in complex numerical simulations of its magnetic structure: while the magnetic field aligns the copper ions’ magnetic moments on the tips of the sawtooth chains along the field and thus reduces the frustration as expected, it is precisely these magnetic moments that mediate a weak coupling to neighboring chains. When this is removed, a long-range magnetic order can no longer exist. This also provided the team with an explanation for the particularly strong magnetocaloric effect: it always occurs when a magnetic field influences the disorder – or more precisely, the magnetic entropy – of a system. In order to compensate for this rapid change in entropy, the material has to adjust its temperature accordingly. This is the very mechanism the researchers have now managed to demonstrate in atacamite.

“Of course, we do not expect atacamite to be extensively mined in the future for use in new cooling systems,” says Dr. Tommy Kotte, “but the physical mechanism we have investigated is fundamentally new and the magnetocaloric effect we observed is surprisingly strong.” The team hopes their work will inspire further research, especially a targeted search for innovative magnetocaloric materials within the extensive class of magnetically frustrated systems.

Publication:
L. Heinze, T. Kotte, R. Rausch, A. Demuer, S. Luther, R. Feyerherm, E. L. Q. N. Ammerlaan, U. Zeitler, D. I. Gorbunov, M. Uhlarz, K. C. Rule, A. U. B. Wolter, H. Kühne, J. Wosnitza, C. Karrasch, S. Süllow, Atacamite Cu₂Cl(OH)₃ in High Magnetic Fields: Quantum Criticality and Dimensional Reduction of a Sawtooth-Chain Compound, in Physical Review Letters, 2025 (DOI: 10.1103/PhysRevLett.134.216701)

Additional information:
Dr. Leonie Heinze
Institute of Condensed Matter Physics
TU Braunschweig

and
Jülich Centre for Neutron Science (JCNS) at the Heinz Maier-Leibnitz Zentrum (MLZ)
Forschungszentrum Jülich GmbH
Phone:  +49 89 158860 811| Email: l.heinze@fz-juelich.de

Prof. Dr. Stefan Süllow
Institute of Condensed Matter Physics
TU Braunschweig
Phone: +49 531 391-5116 | Email: s.suellow@tu-braunschweig.de

Dr. Tommy Kotte
High Magnetic Field Laboratory Dresden at HZDR
Phone: +49 351 260 2564 | Email: t.kotte@hzdr.de

Medienkontakt:
Simon Schmitt | Head
Communications and Media Relations at HZDR
Phone: +49 351 260 3400 | Mob.: +49 175 874 2865 | Email: s.schmitt@hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:

• How can energy and resources be utilized in an efficient, safe, and sustainable way?
• How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
• How do matter and materials behave under the influence of strong fields and in smallest dimensions?

To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources.
HZDR is a member of the Helmholtz Association and has six sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 680 are scientists, including 200 Ph.D. candidates.

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Journal

Physical Review Letters

DOI

10.1103/PhysRevLett.134.216701 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Atacamite Cu₂Cl(OH)₃ in High Magnetic Fields: Quantum Criticality and Dimensional Reduction of a Sawtooth-Chain Compound

 

Here are the flowers that both bees and humans like best

Botanists from the University of Copenhagen and the UK set out to find the best flower combinations for bees and hoverflies.

University of Copenhagen - Faculty of Science

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Here are the flowers that both bees and humans like best

Botanists from the University of Copenhagen and the UK set out to find the best flower combinations for bees and hoverflies. The results make it easier for garden owners and municipalities, among others, to plant the perfect pantries for insects, which also delight the human eye.

Flower strips, seed mixtures, and wild by design. We want to help bees and other vital pollinators, which are in decline all over the world. But which flowers are actually the best?

This question prompted botanists from the Natural History Museum of Denmark at the University of Copenhagen and botanists from the National Botanic Garden of Wales to conduct a scientific study of which flower mixtures attract the most pollinators.

“Much of our knowledge in this area is anecdotal. So, there was a need for a scientific approach, where we systematically test different flowers to be sure how we can best help pollinators, which are extremely important to our ecosystems,” says professor and botanist Natasha de Vere from the Natural History Museum of Denmark.

Yarrow, Garden cosmos, and cornflower are a treat

The researchers reviewed over 400 previous research articles on flowers and insects and investigated how much bees and hoverflies like the finished flower mixtures that are currently sold commercially.

Based on the study, the researchers developed two new seed mixtures, which they evaluated both on the number of insects that visited them and on their aesthetic appeal to humans.

“We can see that seed mixtures containing both non-native and native flowering plants establish themselves better in the soil, bloom for longer, and have more visits from pollinators. And they are also most attractive to the human eye,” says Natasha de Vere.

Based on the study, the researchers recommend choosing seed mixtures with these species if you want to attract bees and hoverflies and are also interested in the aesthetic value of the flowers:

•    Yarrow (Achillea millefolium)

•    Corn chamomile (Anthemis arvensis)

•    Cornflower (Centaurea cyanus)

•    Purple viper's bugloss (Echium plantagineum)

•    Corn marigold (Glebionis segetum)

•    Common poppy (Papaer rhoeas)

•    Field mustard (Sinapis arvensis)

•    Scentless chamomile (Tripleurospermum inordorum)

•    Garden cosmos (Cosmos bipinnatus)

•    Moroccan toadflax (Linaria maroccana)

•    Common phacelia (Phacelia tanacetifolia)

If everyone does a little, we can help the bees

The reason why the researchers have also included the aesthetic dimension of flower mixtures in their study is, of course, that appearance also has a significant impact on what we choose to plant in our gardens and green spaces.

"It has become quite popular to plant strips of flowers in urban areas and in gardens where there may have been only grass lawns before. This is because flowers are good for bees, but also for our mental health," says Natasha de Vere.

According to the professor, who has conducted in-depth research into the interaction between plants and pollinators for a number of years, even small areas of flowers are of great importance to our buzzing friends.

Her research shows that gardens and urban areas can be very good for pollinators.

“It is important that everyone does something to help – and even small changes can really make a difference. I myself only have a small backyard, which I have filled with the best plants for pollinators, and it is now full of bees and hoverflies,” she says, adding:

“I hope our new research results can be used to provide evidence-based guidance on how to select plant species – whether you are a garden owner, a municipal gardener, or otherwise involved in producing seed mixtures.”

Contact:

Michael Skov Jensen
Press officer
University of Copenhagen

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Journal

Plants People Planet

DOI

10.1002/ppp3.70041 

Article Title

The pick of the plot: An evidence-based approach for selecting and testing suitable plants to use in annual seed mixes to attract insect pollinators

Article Publication Date

24-Jun-2025

 

Removing out-of-pocket fee improves access to 3D mammography

Eliminating patient costs also reduced healthcare disparities

University of California - Los Angeles Health Sciences

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UCLA Health radiologist Dr. Tiffany Chan reviews mammogram

Credit: Milo Mitchell/UCLA Health

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Credit: Milo Mitchell/UCLA Health

A new study by UCLA researchers shows that removing a modest $45 out-of-pocket fee significantly improved access to digital breast tomosynthesis (3D mammography), an advanced breast cancer screening technology. Researchers found that eliminating the fee increased overall usage several percentage points and particularly benefited underserved patient populations, including racial and ethnic minorities and non-English speakers. The study appears in the Journal of the American College of Radiology.

Why it matters

Even small financial barriers can prevent patients from accessing potentially life-saving medical technology. Digital breast tomosynthesis provides more detailed breast images than traditional mammography, improving cancer detection while reducing false positives. Ensuring equitable access to the best available screening technology is critical for reducing health disparities. The new study provides concrete evidence that eliminating patient cost-sharing can be an effective policy tool for improving healthcare equity.

What the study did

Researchers analyzed screening mammography data from 13,284 women at a multi-site academic institution between March 2018 and August 2022. The institution had implemented a $45 patient fee for digital breast tomosynthesis that was refunded if insurance later covered the procedure. This fee was eliminated in January 2021 because most insurers were providing full coverage. Of note, all patients in the study were imaged at sites with digital breast tomosynthesis available, thus women had the option of choosing DBT or 2D mammogram. The research team used a statistical method called difference-in-difference analysis, which compares how different patient groups changed over time relative to each other, helping isolate the specific impact of the fee removal from other factors that might have influenced screening choices, examining how the institutional change affected different patient groups based on race, ethnicity, language, insurance type, and socioeconomic status.

What they found

Overall digital breast tomosynthesis utilization increased by 7.8 percentage points after fee elimination (from 83.7% to 91.5%). The benefits were particularly pronounced among historically underserved groups: Asian, Black, and Hispanic patients showed additional increases of 5.0, 6.2, and 6.2 percentage points respectively beyond the gains seen in white patients. Non-English-speaking patients experienced a 7.1 percentage point greater increase than English-speaking patients. Patients with Medicaid insurance and those from more socioeconomically disadvantaged areas also showed greater improvements in access. Despite these gains, some disparities persisted, indicating that additional strategies beyond fee removal may be needed.

From the experts

"These findings demonstrate that even modest out-of-pocket costs can create meaningful barriers to accessing advanced screening technology," said Nina M. Capiro, MD, lead author and diagnostic radiologist at UCLA Health. "While we saw encouraging improvements across all groups after removing the fee, persistent disparities indicate that additional approaches are needed to ensure truly equitable access. This research shows how policy changes can have measurable impacts on health equity, but it also reminds us that eliminating financial barriers alone may not be sufficient to address all access challenges."

What's next

The findings suggest that healthcare systems should examine how patient cost-sharing affects utilization of advanced medical technologies. Future research could explore what additional interventions might be needed to fully eliminate disparities in access to digital breast tomosynthesis and other screening technologies. Healthcare policymakers may also consider these results when designing insurance coverage policies and patient financial assistance programs. The study provides a model for evaluating the equity impacts of healthcare financing decisions.

About the study: Effect of Fee Removal on the Usage of Digital Breast Tomosynthesis to Minimize Healthcare Disparities, Journal of the American College of Radiology 2025, DOI: 10.1016/j.jacr.2025.06.022.

About the Research Team Nina Capiro, James Sayre, and Anne Hoyt, all from the Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles; Prasidda Khadka, David Geffen School of Medicine, University of California, Los Angeles; Gelareh Sadigh, Department of Radiological Sciences, University of California, Irvine.

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Journal

Journal of the American College of Radiology

DOI

10.1016/j.jacr.2025.06.022 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Effect of Fee Removal on the Usage of Digital Breast Tomosynthesis to Minimize Healthcare Disparities

Article Publication Date

26-Jun-2025

 

CABI-led study suggests women in Pakistan need greater access to information on parthenium weed

A new CABI-led study investigated smallholder farmers’ knowledge, attitudes and practices towards parthenium and biological control in Pakistan.

CABI

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A farmer tackles parthenium in Pakistan

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Credit: Asim Hafeez for CABI

A new CABI-led study investigated smallholder farmers’ knowledge, attitudes and practices towards parthenium and biological control in Pakistan.

The study brings attention to important gendered aspects of parthenium impact. It also highlights smallholder farmers’ significant role, through their on-farm management practices, in improving the establishment and effectiveness of biological control agents.

The researchers, who sought a gendered perspective for their findings, recommend that increasing women’s access to information on parthenium would improve their knowledge of the weed, effective management approaches, and ways to protect their own and their family members health.

Parthenium hysterophorus L. (Asteraceae) (parthenium weed) has rapidly become one of the world’s worst weeds, responsible for a multitude of negative impacts on crop and pasture production, the environment and human and animal health.

Parthenium, considered one of the ‘100 most invasive species in the world’ by the IUCN, has invaded more than 50 countries, including Pakistan

Parthenium is native to Central and South America, Mexico, and the Caribbean, and has become invasive in much of the world. This invasive weed has now invaded more than 50 countries, including Pakistan, and threatens to invade many more, exacerbated further by a changing climate.

In Pakistan, parthenium is a major weed that is displacing native flora, competing with agricultural crops, and causing health concerns for both humans and livestock. Parthenium weed affects human health from skin irritation, fever and breathing problems since the inhalation of certain airborne particles including fine hairs and pollen, can result in an allergic response, leading to hay fever, bronchitis or asthma.

The impacts on livestock include digestive problems from ingesting the weed, skin irritations/sores, reduced hunger, reduced weight, and tainted milk and meat.

An integrated management approach is widely acknowledged as the most effective strategy to manage pests, including weeds. As part of an integrated approach, classical biological control offers a highly sustainable management option whereby self-perpetuating populations of control agents establish throughout the target weed’s range.

Biological control offers a long-term sustainable solution but requires farmer engagement and support through a coordinated area-wide management approach. The approval for the stem-boring weevil, Listronotus setosipennis, to be released as a classical biological control agent for parthenium in Pakistan, was a significant achievement.

Knowledge, attitudes and practices towards parthenium and biological control

The scientists, whose research was published in the journal CABI Agriculture and Bioscience, sought to investigate men and women smallholder farmers’ knowledge, attitudes and practices towards parthenium and biological control. The release of L. setosipennis provided an opportunity to gather a comprehensive baseline that will be crucial to measuring change in farmers knowledge, attitudes and practices towards biological control as the programme progresses.

During the study household surveys using a structured questionnaire took place with 562 farmers (62% men and 38% women) in Khyber Pakhtunkhwa, Punjab and Azad Jammu and Kashmir (AJK).

This was complemented by seven focus group discussions with separate men and women’s groups in each district and key informant interviews with 17 extension agents and 31 agro dealers. A mixed-methods approach, utilising both quantitative and qualitative methods, allows researchers to gain a more comprehensive understanding of the problem.

In all survey areas, women and men farmers reported parthenium present on their farming land, abundant on common land, and rapidly spreading.

Women reported higher levels of land covered by parthenium, likely due to their frequent presence within the field whilst hand weeding. Women, and farmers in Khyber Pakhtunkhwa, more frequently reported negative health effects due to contact with parthenium.

The two key management methods used for parthenium were hand weeding and chemical herbicides, the former used more frequently by women. Additionally, the awareness of the risks of the latter were lower amongst women. However, both men and women were open to using biological control as an alternative method of management.

Extension agents have an important role in advising farmers

Kate Constantine, an author of the study and Project Scientist at CABI, said, “Extension agents have an important role in advising farmers and promoting the use of alternatives such as biological control, but women do not engage in many extension activities.

“Biological control of parthenium using L. setisopennis offers an opportunity to engage with farmers and strengthen their knowledge of biological control while demonstrating its use at a landscape level. Targeted awareness campaigns using face-to-face and other verbal methods of communication are recommended for enhancing the farmers’ knowledge base and encouraging a change in practices over time.”

The scientists found that women have less access to extension agents or training and are less likely to belong to groups since social norms largely determine that men engage in extension activities or trainings.

This is exacerbated when land size and ownership are common criteria for selecting training participants disadvantaging women who often do not own land and have smaller farms.

Dr Philip Weyl, a co-author of the paper and Head of Weed Biological Control at CABI, said, “Farmers are spending limited resources on parthenium management, not to mention additional costs for medicine or for employing labourers when health effects are experienced.

“In addition, family labour is highlighted as important in parthenium control with the estimated amount presented in this study likely to be underestimated. Area-wide biological control of parthenium could potentially ease these burdens if L. setisopennis establishes and spreads at a landscape level.”

The scientists conclude that increasing women’s access to information and training would improve their knowledge of parthenium and effective management approaches, including how to support L. setisopennis to establish, and ways to protect their own and their family members’ health.

Additional information

Main image: A woman farmer feeding parthenium to her livestock (Credit: Ms. Asiya Iqbal for CABI)

Full paper reference

Constantine, Kate and Rehman, Abdul and Faisal, Shah and Shah, Maila Al Saba and Danish, Muhammad and Weyl, Philip and Tambo, Justice and Ishii-Adajar, Hideo and Williams, Frances, ‘Smallholder farmers’ knowledge, attitudes and practices towards parthenium and biological control in Pakistan: A gendered perspective,’ CABI Agriculture and Bioscience, 26 June 2025. DOI:10.1079/ab.2025.0046

The paper can be read in full here: https://doi.org/10.1079/ab.2025.0046

Relevant stories

‘Biocontrol agent released to control noxious parthenium weed in Pakistan.’

‘CABI’s new quarantine facility creates greater capacity for Parthenium research in Pakistan.’

‘CABI publishes recommendations to fight scourge of parthenium weed in Central West Asia.’

Funding statement

This research was funded by the CABI-led PlantwisePlus programme, which is financially supported by Directorate-General for International Cooperation (DGIS), Netherlands; European Commission Directorate General for International Partnerships (INTPA, EU); the Foreign, Commonwealth & Development Office (FCDO), United Kingdom; the Swiss Agency for Development and Cooperation (SDC); and the Australian Centre for International Agricultural Research (ACIAR).

CABI is an international intergovernmental organization, and we gratefully acknowledge the core financial support from our member countries (and lead agencies), including the United Kingdom (Foreign, Commonwealth and Development Office), China (Chinese Ministry of Agriculture and Rural Affairs), Australia (Australian Centre for International Agricultural Research), Canada (Agriculture and Agri-Food Canada), the Netherlands (Directorate-General for International Cooperation), Switzerland (Swiss Agency for Development and Cooperation) and Ireland (Irish Aid, International Fund for Agricultural Development-IFAD). See http://www.cabi.org/ about-cabi/who-we-work-with/key-donors/ for full details.

A woman farmer feeding parthenium to her livestock

Credit

Ms. Asiya Iqbal for CABI

Journal

CABI Agriculture and Bioscience

DOI

10.1079/ab.2025.0046 

Method of Research

Experimental study

Subject of Research

People

Article Title

Smallholder farmers’ knowledge, attitudes and practices towards parthenium and biological control in Pakistan: A gendered perspective

Article Publication Date

26-Jun-2025