Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Metal with unusual properties


A Chinese-German research cooperation involving the University of Augsburg has demonstrated properties in a metal that cannot be explained by the standard theory. The results were obtained on a special metallic compound with unusual magnetic characteristics – scientists call it mag-netic frustration. The cooperation observed a novel, “quantum critical behaviour” in the metal at very low temperatures and at high pressures and strong magnetic fields.

Metals are elements or compounds that conduct electrical current. As the brilliant Russian phys-icist Lev Landau already identified in the 1950s, their properties can be interpreted as if almost independently-movable charge carriers act.

Temperature pressure/magnetic field phase diagram for the CePdAl compound. The colour cod-ing indicates the temperature behaviour of the electrical resistance.

Nature Physics

Landau called them “quasiparticles” to indicate that they describe a collective state only, in contrast to ordinary electrons.

However, in recent years, materials with properties that are more complex and cannot be de-scribed by Landau’s quasiparticle model have been attracting attention. This also includes the high-temperature superconductors that are interesting for their potential applications.

The qua-siparticle picture breaks down when the ground state of a metal – its phase – changes in the event of an external disturbance, such as the application of pressure or a magnetic field.

This change can be, for example, that the magnetic moments in the metal (in simplified terms: the elementary magnets) point in completely different directions down to the lowest temperatures (normally they are aligned at low temperatures, i.e. they are in an ordered state).

The result is an exotic metallic state, the quantum critical point – named as such because it usually only oc-curs under strictly defined conditions in what is known as the phase diagram. Quantum critical points underly unusual phases such as high-temperature superconductivity.

The Chinese-German team has now demonstrated for the first time with measurements how not only an individual point, but an entire area in the phase diagram can show quantum-critical be-haviour. For this purpose, they have examined a metallic compound made up of the elements cerium, palladium and aluminium (chemical abbreviation: CePdAl) through a detailed study.

The Augsburg group led by Prof. Dr. Philipp Gegenwart has investigated the heat capacity of samples intentionally contaminated (doped) with atoms of foreign atoms at low temperatures. The re-searchers led by Prof. Dr. Peijie Sun of the Institute of Physics in Beijing also measured how the electrical resistance of CePdAl changes under pressure and in a magnetic field.

By combining all data, the cooperation was able to prove that CePdAl has a broader critical area instead of a singular critical point. The researchers suspect that this is due to the special ar-rangement of magnetic moments in CePdAl. The cerium atoms, responsible for the magnetism, are arranged in a kind of triangular pattern. The consequence of this pattern is a special phe-nomenon, the “magnetic frustration”.

The cerium electrons behave like small magnets and want to align their magnetic poles with their nearest neighbours at low temperatures. In the CePdAl compound, however, the usual mutual anti-parallel alignment is impossible due to a triangular arrangement.

Only two magnets in the triangle can be antiparallel to each other, the third one cannot be antiparallel to both of the others at the same time. “We suspect that this frustration effect stabilises the quantum crit-ical area,” explains Gegenwart.

The success of the study is the result of a cooperation between institutes in Germany and China, supported by the German Research Foundation (Deutsche Forschungsgemeinschaft – DFG) and its Chinese partner organisation.

The results are not only important for fundamental research, but they are also relevant for a better understanding of the high temperature superconductivity and other phenomena with potential for various applications.

Magnetic frustration could be the key to understanding critical metallic states that have been observed previously in other materials. “This important conclusion has only become possible thanks to the highly sensitive measurements in Augsburg and Beijing,” said Prof. Dr. Alois Loidl from the University of Augsburg, German spokesperson for the Chinese-German cooperation project.

The “Sino-German Cooperation Group” with groups from Hangzhou, Beijing, Frankfurt and Augsburg enables intensive scientific exchange of the participating working groups in China and Germany thus promoting excellent cutting-edge research.

Temperature pressure/magnetic field phase diagram for the CePdAl compound. The colour cod-ing indicates the temperature behaviour of the electrical resistance. The metal behaves as ex-pected wihtin the red marked regions, while deviation from theory becomes from yellow through green towards blue more and more pronounced. The main result is the existence of a quantum critical phase (centre). The atomic structure of the CdPdAl crystal (above) may be re-sponsible for its stabilisation.

Wissenschaftliche Ansprechpartner:

Prof. Dr. Philipp Gegenwart, Lehrstuhl für Experimentalphysik VI
+49 (0)821 598-3650, philipp.gegewart@physik.uni‐

Prof. Dr. Alois Loidl, Lehrstuhl für Experimentalphysik V
+49 (0)821 598--3751, alois.loidl@physik.uni‐


Hengcan Zhao, Jiahao Zhang, Meng Lyu, Sebastian Bachus, Yoshifumi Tokiwa, Philipp Gegenwart, Shuai Zhang, Jinguang Cheng, Yi-feng Yang, Genfu Chen, Yosikazu Isikawa, Qimiao Si, Frank Steglich and Peijie Sun, Quantum-critical phase from frustrated magnetism in a strongly correlated metal, Nat. Phys. 15 (2019) 1261, DOI: 10.1038/s41567-019-0666-6

Michael Hallermayer | idw - Informationsdienst Wissenschaft
Further information:

More articles from Physics and Astronomy:

nachricht From China to the South Pole: Joining forces to solve the neutrino mass puzzle
25.02.2020 | Johannes Gutenberg-Universität Mainz

nachricht Beyond the brim, Sombrero Galaxy's halo suggests turbulent past
21.02.2020 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: High-pressure scientists in Bayreuth discover promising material for information technology

Researchers at the University of Bayreuth have discovered an unusual material: When cooled down to two degrees Celsius, its crystal structure and electronic properties change abruptly and significantly. In this new state, the distances between iron atoms can be tailored with the help of light beams. This opens up intriguing possibilities for application in the field of information technology. The scientists have presented their discovery in the journal "Angewandte Chemie - International Edition". The new findings are the result of close cooperation with partnering facilities in Augsburg, Dresden, Hamburg, and Moscow.

The material is an unusual form of iron oxide with the formula Fe₅O₆. The researchers produced it at a pressure of 15 gigapascals in a high-pressure laboratory...

Im Focus: From China to the South Pole: Joining forces to solve the neutrino mass puzzle

Study by Mainz physicists indicates that the next generation of neutrino experiments may well find the answer to one of the most pressing issues in neutrino physics

Among the most exciting challenges in modern physics is the identification of the neutrino mass ordering. Physicists from the Cluster of Excellence PRISMA+ at...

Im Focus: Therapies without drugs

Fraunhofer researchers are investigating the potential of microimplants to stimulate nerve cells and treat chronic conditions like asthma, diabetes, or Parkinson’s disease. Find out what makes this form of treatment so appealing and which challenges the researchers still have to master.

A study by the Robert Koch Institute has found that one in four women will suffer from weak bladders at some point in their lives. Treatments of this condition...

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

Latest News

Turbomachine expander offers efficient, safe strategy for heating, cooling

25.02.2020 | Power and Electrical Engineering

The seismicity of Mars

25.02.2020 | Earth Sciences

Cancer cachexia: Extracellular ligand helps to prevent muscle loss

25.02.2020 | Life Sciences

Science & Research
Overview of more VideoLinks >>>