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Molecular trick alters rules of attraction for non-magnetic metals

6 August 2015

For the first time scientists have demonstrated how to generate magnetism in metals, that aren’t naturally magnetic, which could end our reliance on some rare and toxic elements currently used.

In a recent study researchers from the School of Physics and Astronomy at Leeds have detailed a way of altering the quantum interactions of matter in order to “fiddle the numbers” in a mathematical equation that determines whether elements are magnetic, called the Stoner Criterion.

Being able to generate magnetism in materials that are not naturally magnetic opens new paths to devices that use abundant and hazardless elements, such as carbon and copper. Magnets are used in many industrial and technological applications, including power generation in wind turbines, memory storage in hard disks and in medical imaging. Yet, despite their widespread use, at room temperature only three elements are ferromagnetic – meaning they have high susceptibility to becoming and remaining magnetic in the absence of a field, as opposed to paramagnetic substances, which are only weakly attracted to the poles of a magnet and do not retain any magnetism on their own. These ferromagnetic elements are the metals iron, cobalt and nickel.

Having such a small variety of magnetic materials limits the ability to tailor magnetic systems to the needs of applications without using very rare or toxic materials. Having to build devices with only the three magnetic metals naturally available to us is rather like trying to build a skyscraper using only wrought iron. Why not add a little carbon and make steel?

Future technologies, such as quantum computers, will require a new breed of magnets with additional properties to increase storage and processing capabilities. The research at Leeds has taken a step towards creating such ‘magnetic metamaterials’ that can fulfil this need.

The condition that determines whether a substance is ferromagnetic is called the Stoner Criterion.  It explains why iron is ferromagnetic while manganese is not, even though the elements are found side-by-side in the periodic table. The Stoner Criterion was formulated by Professor Edmund Clifton Stoner, a theoretical physicist who worked at the University of Leeds from the 1930s until the 60s. At its heart, it analyses the distribution of electrons in an atom and the strength of the interaction between them. It states that for an element to be ferromagnetic, when you multiply the number of different states that electrons are allowed to occupy in orbitals around the nucleus of an atom – called the Density of States (DOS) – by something called the ‘exchange interaction’, the result must be greater than one.

The exchange interaction refers to the magnetic interaction between electrons within an atom, which is determined by the orientation of each electron’s magnetic ‘spin’ – a quantum mechanical property  to describe the intrinsic angular momentum carried by elementary particles, with only two options, either ‘up’ or ‘down’.

In the new study, the researchers have shown how to change the exchange interaction and DOS in non-magnetic materials by removing some electrons using an interface coated with a thin layer of the carbon molecule C60, which is also called a ‘buckyball’. The movement of electrons between the metal and the molecules allows the non-magnetic material to overcome the Stoner Criterion.

Researchers had previously noticed that creating a molecular interface changed how magnets behave. The next step was to test if molecules could also be used to bring magnetic ordering into non-magnetic metals and the researchers at Leeds have successfully demonstrated the technique, but further work is needed to make these synthetic magnets stronger. Researchers are confident that applying the technique to the right combination of elements will yield a new form of designer magnets for current and future technologies.

This research, led by Dr Oscar Cespedes as principle investigator, was funded by the Engineering and Physical Sciences Research Council (EPSRC) and published in a paper, ‘Beating the Stoner Criterion Using Molecular Interfaces’, in the journal Nature on 6 August 2015, with co-lead authors Fatma Al Ma’Mari and Tim Moorsom.

Ogden Trust Physics Summer School

24 July 2015

The School of Physics and Astronomy hosted a 4 day Ogden Trust Physics Summer School this week, with 30 AS-level physics students from across the wide Yorkshire area attending. The event was aimed at high achieving students, and included a mix of workshops and lectures designed to challenge and improve their mathematical skills.

Students also had the opportunity to join research groups in the School for a day, visiting research laboratories and gaining experience of using state-of-the-art equipment. This included spectrometers, x-ray diffractometers, liquid crystals and single molecule force spectroscopy.

Physics Graduation

20 July 2015

Congratulations to all our 2015 graduates!

On Tuesday 14th July 2015, finalists of both undergraduate and postgraduate study graduated from the School of Physics and Astronomy. Lord Bragg gave an inspiring speech before the ceremony began, followed by the presentation of degrees. Finalists and their families were then invited to attend a reception at the Refectory, it was a fantastic opportunity for staff, students and families to meet and celebrate the fantastic achievements of our students.
Congratulations to everyone who graduated and best of luck with your futures!

Soapbox Science

22 June 2015

On 20th June Dr Lorna Dougan joined eleven other scientists to take part in ‘Soapbox Science’ in Belfast.

Soapbox Science is a novel public outreach platform for promoting women scientists and the science they do. These events transform public areas into an arena for public learning and scientific debate; following the format of London Hyde Park’s Speaker’s Corner, which is historically an arena for public debate. With Soapbox Science, everyone has the opportunity to enjoy, learn from, heckle, question, probe, interact with and be inspired by leading scientists.

At the event, which attracted ~2000 people, Lorna presented her research on ‘Using physics to explore life in extreme environments’. This included an introduction to the world of extremophiles, single molecule force spectroscopy and demonstrations of polymer collapse and protein folding. To find out more about Soapbox Science please visit:

Dr Lorna Dougan would like to thank the Science & Technology Facilities Council (STFC) who sponsored her attendance at Soapbox Science, as well as the European Research Council (ERC) who fund her research on ‘Extreme Biophysics’.

Soft Matter Away Day

13 May 2015

The School recently hosted a Soft Matter Physics away day at Weetwood Hall. The day was chaired by Professor Helen Gleeson, the new Head of the Soft Matter Physics group, and soon to be, new Head of School.

It was a fantastic opportunity for Professor Gleeson, Professor Jones and Dr Nagaraj, who have all joined the School from the University of Manchester, to meet with fellow researchers in the field of Soft Matter. Members from across the Faculty and University attended, with representatives from MaPS, Biological Sciences, Engineering and Design, in addition to others.

Each delegate gave a brief overview of their work, which was followed up by discussion, presentations from Ben Williams and Rachel Woolley, Research & Innovation Service, which included H2020, links with N8 and RCUK strategic priorities.

Overall, the day was a great success, there were some fantastic discussions, innovative ideas and hope for some future collaborations.

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