AG Wende - Welcome

Welcome to the group of Prof. Wende Magnetic nanostructures

Address

Universität Duisburg-Essen
Fakultät für Physik
Experimentalphysik - AG Wende
Lotharstr. 1
47057 Duisburg


Head of group

Prof. Dr. Heiko Wende
room: MD 464
phone: +49 (0)203 379 2838
heiko.wende@uni-due.de


Office

Christiane Leuchtenberger
room: MD 465
phone: +49 (0)203 379 2385
fax: +49 (0)203 379 3601
christiane.leuchtenberger@uni-due.de

31.01.2019 Symposium awarded to PhD students

Young scientists of the UDE and the Jülich Research Centre were successful in the procurement of a symposium during Europe's largest congress of physicists. Their interdisciplinary topic "Biogenic Spin Phenomena" was selected from all submitted proposals. Participants of the Spring Meeting of the German Physical Society (DPG) can visit the symposium on the 3rd of April, free of charge and without prior appointment.

20.12.2018 Prof. Heiko Wende elected as new scientific director of CENIDE

During the CENIDE board meeting on the 19th of December, Prof. Heiko Wende was elected as the new scientific director, while Prof. Malte Behrens was appointed as deputy.

17.05.18 New Collaborative Research Collective involving Prof. Heiko Wende and Prof. Rossitza Pentcheva from our faculty

Nanotechnology and catalysis research are united in a new Collaborative Research Collective that will be established at the University of Duisburg-Essen (UDE) and the Ruhr-University Bochum (RUB) this July, as announced by the German Research Foundation (DFG). This new network ("Heterogeneous oxide catalysis in the liquid phase"), under the auspices of the University Alliance Ruhr (UA Ruhr), will be funded with ca 10 Mio. Euro for four years at first.

23.04.18 Research results of the AG Wende shown on the cover of Annalen der Physik

Magnetite nanoparticles are utilized for both basic research, as well as application purposes, thanks to their interesting inherent properties. Such iron oxide nanoparticles are already being used as contrast agents for magnetic resonance imaging (MRI), for cancer treatments via hyperthermia, for the controlled in vivo transport of medication, adjustable automotive shock absorbers, magnetic ink for printers, and also for the removal of heavy metals from wastewater. Magnetite is distinguished by a  phase transition at 123 K (- 150°C), the Verwey transition.

It is difficult to characterize this phase transition in an ensemble of nanoparticles via diffraction methods. In a cooperation between Dr. Carolin Schmitz-Antoniak (FZ Jülich), members of the AG Wende and theoreticians from the Uppsala University (Sweden), the Verwey transition in nanoparticles was successfully analyzed in detail using X-ray absorption spectroscopy at the synchrotron radiation source BESSY-II in Berlin. Interestingly, it was found that the Verwey transition can be suppressed by a shell of silica (of which an artistic representation is shown on the cover of the renowned journal "Annalen der Physik"). Using spectroscopic investigations, this effect was explained by the trapping (retaining) of charges by the interfaces between the silica shells and the iron oxide nanopartices. This new insight opens up possibilities for the tailoring of nanoparticle properties for new applications, such as smart materials.

© CENIDE

21.02.18 Dr. Joachim Landers receives CENIDE presentation prize

The yearly CENIDE conference was held between the 19th and 21st of January in Bergisch Gladbach. During this event, the best presentations from the Young Researcher Session were awarded with prizes. Dr. Joachim Landers (2nd from right) was also among the prize winners, with his presentation "Simultaneous Study of Brownian and Néel Relaxation Phenomena in Ferrofluids by Mössbauer Spectroscopy".

Photo: Uta Filippich

05.02.18 Microseminar prizes awarded at the Edgar-Lüscher-Seminar

The traditional microseminar prizes were awarded at this year's Edgar-Lüscher-Seminar in Klosters. These honor the best poster presentations that have to be held within a very short time limit. Among the five awardees, prizes were received by Nico Rothenbach (2nd from left) and Alexandra Terwey (2nd from left), with the ceremony being headed by Eberhard Wassermann (3rd from left) and the general secretary of the German Research Foundation (DFG) Dorothee Dzwonnek (3rd from right).

UHV-PLD in LN 2.46

25.01.18 Groups Wende and Farle put new UHV-PLD setup into operation

A new UHV-PLD system in the NETZ building was commissioned on the 25th of January after extensive preparations. The setup, jointly used by the groups Wende and Farle, combines a UHV chamber that was made available by the University of Ulm with a new Excimer laser from Coherent, which was acquired with financial support from CENIDE. Apart from the possibility of using very low pressures during preparation, this chamber allows a great deal of flexibility for sample preparation. The decisive factor is the computer controlled selection of target materials, enabling the production of complex alloys, composites and multilayers.

This chamber will be used for the newly established CRC/TRR 247 in order to compose reference systems for catalysis studies.

© Sparkasse Duisburg

17.10.17 Prize of the Sparkasse Duisburg awarded to Dr. Joachim Landers

Five students and four PhD students were honored by the Sparkasse of Duisburg for their outstanding achievements, receiving prizes of 1.000 and 2.000€, respectively.

Igor Kozeletskyi (business studies), Christoph Kern (social sciences), Jennifer Stemmann (engineering) and Joachim Landers (physics, AG Wende) received the award for their dissertations, which were graded with summa cum laude. Priyanha Logeswaran (business studies), Lukas Fiege (social sciences), Janosch Luttmer (engineering), Alina Behrendt (mathematics) and Magdulin Dwedari (physics) were honored for their exceptional course achievements.

Photo (from left): Sebastian Reicherts (chair of mechatronics), mayor Manfred Osenger, Joachim Landers, Magdulin Dwedari, Rektor Prof. Ulrich Radtke, Dr. Joachim Bonn, chairman of the Sparkasse Duisburg, Igor Kozeletskyi, Christoph Kern, Alina Behrendt, Jennifer Stemmann and Priyanha Logeswaran.

Groups Wende and Bovensiepen on the peak of the Kogelseespitze

20.08.17 WE-Heraeus-Retreat

The 4-day retreat titled "Solid State Spectroscopy in the Frequency and Time Domain" commenced on the 20th of August at the Hanauer Hütte of the DAV, in the spectacular terrain of the Lechtal Alps, with 22 participants from the groups Wende and Bovensiepen.

The goal of this "Hüttenseminar" was the strengthening of the cooperation between these two groups, which was already achieved during the required mutual support during the initial ascent. The retreat was characterized by hiking tours during several mornings as well as presentations in the afternoons, which were held in English, following topics of a pre-determined scientific programme.

A highlight of the event was the Heraeus-Buffet, which was set up with great care and commitment by the staff of the Hanauer Hütte. The outstanding cooperation between the inkeepers and the visitors clearly shows that this location can be wholeheartedly recommended for such activities.
 

Award ceremony with (from left) Klaus Zimmermann, Günther Aurnhammer, the awardees Rudolf Weber and Joachim Landers, as well as Silvio Dutz und Stefan Odenbach (Photo: Malte Schümann)

18.07.17 Dr. Joachim Landers receives dissertation prize of the German Ferrofluid Society

In the course of the 16th German Ferrofluid Workshop, outstanding dissertations were awarded the 1.000€ Dissertation Prize of the German Ferrofluid Society.

Dr. Joachim Landers of the AG Wende is also among the awardees, with his dissertation "Study of magnetic relaxation dynamics in soft matter nanoparticle composite systems".

© CENIDE

23.11.16 Yearly CENIDE Celebration

With the Kreuzeskirche in Essen being chosen as an unusual location, around 120 members and staff of CENIDE took part in the venue. Between the high white walls and colorful windows, they informed themselves about the work of their colleagues during the poster session, watched the award ceremony and had a chat about research and everyday life during a buffet of Currywurst, quiche and Co.

Samira Webers of our group was among the prize winners this year, with her poster “Magnetic relaxation effects of raspberry particles in meltable biopolymers”.

12.07.16 Currentless switching of processors

It's a vision of a computer that is both efficient and works without generating heat: A team of scientists, among them those of the Center for Nanointegration (CENIDE) of the University of Duisburg-Essen (UDE), has succeeded in the currentless switching of so called multiferroic clusters. This discovery can represent a further step towards the next generation of microchips and has now been published as leading article in the scientific journal "Advanced Functional Materials".

09.06.16 How do spins communicate with each other?

Members of the Wende research group have analyzed spin-communication channels of magnetic double-decker molecules on ferromagnetic substrates. Their results were so peculiar that they were now published in the journal "Nature Scientific Reports". If the spin changes at one point in space, it causes an influence at another point. The strength of this influence was examined, referred to as coupling, as well as the underlying mechanism of this coupling (see schematic image). It shows a clear antiferromagnetic coupling of the rare earth ions Tb and Dy to the ferromagnetic substrate through the phthalocyanine ligands. This was examined by the element specific magnetization as a function of an applied magnetic field. The precise analysis of this field dependence schows that the Tb ions are more strongly magnetically coupled than the Dy ions. The measurements were performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

A. Candini, D. Klar et al. Nature Scientific Reports 6, 21740 (2016)

31.05.16 New Collaborative Research Centre 1242

The DFG has established a new Collaborative Research Centre at the Faculty of Physics, with Heiko Wende, Uwe Bovensiepen and Alexander Tarasevitch supervising the subproject A5.

This project aims at the combined investigation of the non-equilibrium dynamics in time and space in complex materials after microscopic excitation. To achieve an element selective insight into e. g. Fe/MgO multilayers or Co/CoxOy core shell nanoparticles excitations will be pumped optically by femtosecond pulses and probed resonantly in the soft X-ray range. We will carry out pump-probe experiments with complementary X-ray sources for femtosecond pulses from 1) synchrotron radiation facilities and free-electron lasers and 2) table-top sources at Campus Duisburg. The main goal is the energy transfer dynamics between the components in metal-insulator hetero-structures.

TEM image of coated magnetic nanoparticles. Adapted with permission from J. Landers et al. Nano Lett., 2016, 16 (2), pp 1150–1155, © 2016 American Chemical Society

16.03.16 Small relaxed magnets

Magnetic nanoparticles are real all-rounders: They are utilized for cancer therapy, in loudspeakers or shock absorbers. But so many different applications require very precisely tuned material properties. Researchers around Professor Wende of the Center for Nanointegration (CENIDE) of the University of Duisburg-Essen (UDE) have now analyzed how such particles relax, publishing their results in the renowned journal "Nano Letters". The main focus was on the simultaneous measurement of Brown and Néel relaxation by Mössbauer spectroscopy.

This project is a cooperation of the Priority Programme 1681 of the German Research Foundation and their colleagues at the Technical University of Braunschweig.

16.11.15 Materials, smart and changeable

Functional materials are real multitalents. They are found in a large number of devices nowadays, from the car to the smartphone. The German Research Foundation (DFG) supports their development. For an additional three years, the research group "Ferroic Functional Materials - Multiscale Modeling and Experimental Characterization" (FOR 1509) receives continued funding. This includes two subprojects of physicsts and engineers of the University of Duisburg-Essen being funded with over 750.000 Euros.

To pave the way for further successfull collaborations, the scientists met for a kick-off on the 19th and 20th of November in the NETZ (NanoEnergieTechnikZentrum). Their goal is a new quality in the characterization and modeling of so called smart materials. These functional materials are capable of transforming one physical change into another, such as changes in mechanical strain or temperature using magnetic fields. New tools for modeling are to be developed using an interdisciplinary approach.

The two coordinators, Prof. Dr. Jörg Schröder and Prof. Doru C. Lupascu are jointly researching with Dr. Dominik Brands (faculty of engineering) and Prof. Dr. Heiko Wende (faculty of physics) at the UDE. Further colleagues at the universities of Aachen, Darmstadt, Dortmund, Erlangen-Nürnberg, Kaiserslautern and Stuttgart partake as well. Their expertise encompasses a large theoretical and experimental bandwidth of the functional materials in question.

Four of the seven subprojects are situated at the UDE and the TU Dortmund. These projects show how intensely the Ruhr Valley universities are connected under the roof of the University Alliance ruhr: The universities of Bochum, Dortmund and Duisburg-Essen are linking their expertise in materials and production science under the core profile "Materials Chain". This includes material design and refining all the way to characterization and processing in manufacturing processes in all phases of modern production and material sciences.

10.11.15 New scientific director and deputy for CENIDE

During its 59th session last Wednesday, Prof. Dr.-Ing. Stephan Barcikowski has been elected as the new scientific director by the CENIDE board of management. His colleague Prof. Dr. Heiko Wende was appointed as deputy.

Anharmonic spin structure in Mössbauer spectrum

13.10.14 Magnetic Ordering in Multiferroic Nanoparticles

Scientists of the group of Prof. Wende published an article in NanoLetters, in a CENIDE cooperation with the Institute for Materials Science in Essen.

The paper deals with the properties of BiFeO3 (bismuth ferrite), which is a room temperature multiferroic, but hasn't seen widespread application due to its antiferromagnetic ordering. However, in nanoparticles, the material shows weak ferromagnetism, apparently a size dependent effect, which has already been discussed in a previous cooperation.

In this latest work, special attention was paid to the magnetic ordering of BiFeO3, which has a complex, periodic cycloidal structure with a defined period lenght. By measurements on different sized nanoparticles with Mössbauer-spectroscopy, the temperature dependent behaviour of the spin cycloid could be determined.

Announcement 575th Wilhelm and Else Heraeus seminar: "Functional metalorganics and hybrids"

17 - 19 November 2014, Physikzentrum Bad Honnef (near Bonn), Germany

 

More details and application information:575. Wilhelm und Else Heraeus-Seminar:

29.11.13 Industry and fundamental researchers cooperate on project - More storage density for PCs

In today's world, computer hard disk drives (HDDs) must be able to store enourmous amounts of data, which is slowly turning into a problem for manufacturers: It's hardly possible to increase performance with currently used materials. We, the workgroup Wende of the University of Duisburg-Essen, the Uppsala University and Seagate, a world leading manufacturer of HDDs, are seeking to change this. We want to develop ultra thin layer structures that allow a higher magnetization, without which the reading and writing of information wouldn't be possible. Our project NU-MATHIMO (New Materials for High Moment Poles and Shields) will receive a sponsorship of one million Euros from the EU.

Click here for the press report (German)

Dr. Carolin Schmitz-Antoniak

04.11.13 Dr. Carolin Schmitz-Antoniak takes office as Helmholtz group leader for young scientists

Dr. Carolin Schmitz-Antoniak from our workgroup was able to acquire one of the very well equipped and sought-after positions as Helmholtz junior scientist group leader. She will take office at her new position on the 1st of February 2014 at the Peter Grünberg Institut 6 of the Forschungszentrum Jülich.

In the scope of this program, young scientists receive a yearly sponsorship of 250.000€. These funds enable them to build up and lead their own research group for the first time.

Nanocomposite

26.06.13 Nano duet

Exploiting ferroelectric and ferromagnetic properties of a system interdependend on each other has been in the focus of current research for quite some time. The team of Prof. Heiko Wende, Prof. Wolfgang Kleemann and Dr. Carolin Schmitz-Antoniak succeeded recently using a composit system. The results have been published in "Nature Communications".

more aboutNano duet” (German)

external information on “Nano duet”

Dr. Anne Warland

11.04.13 Anne Warland

recieved her PhD on "Röntgenabsorptionsspektroskopie an Fe-Oxid-Nanopartikeln"

The thesis is available via the publications server of the university.

-> Anne's thesis on DuEPublico

Refrigeration is one of the main sinks of the German and European electricity consumption and accordingly contributes to worldwide CO2 emissions. High reduction potentials are envisaged if caloric effects in solid materials are utilized. The recent discovery of giant entropy changes associated with ferroelastic phase transformations promises higher efficiency. Ferroic transitions enhance the entropy change of magneto-, elasto-, baro- and electro-caloric effects. Furthermore, because the refrigerant is in a solid state, the technology completely eliminates the need for high global-warming potential halofluorocarbon refrigerants.

In order to accelerate research on ferroic cooling DFG decided to establish the priority program SPP 1599 in April 2011. This SPP will address the following major challenges for introducing ferroic materials in practical cooling applications: Understanding of the underlying mechanisms, energy efficiency, effect size, fatigue, and system integration.

Prof. Dr. Peter Entel, Prof. Dr. Michael Farle/Prof. Dr. Mehmet Acet and Prof. Dr. Heiko Wende from our faculty togehter with Prof. Dr. Doru C. Lupascu (Faculty of Engineering, Institute for Materials Science) applied successfully within the new DFG priority programme SPP 1599 and will now contribute to this important research area.

more aboutPriority programme of the DFG:...

During yesterday's general meeting at the Sportschule Wedau, the five winners of the Best Paper Awards and the Photo Competition were honored, also including Dr. Carolin Schmitz-Antoniak and Soma Salamon from our workgroup.

more aboutWinning papers and photos

Dr. Carolin Schmitz-Antoniak

28.08.12 Dr. Carolin Schmitz-Antoniak receives the Dale Sayers Young Scientist Award in Peking

Starting in 2003 the International X-ray Absorption Society (IXAS) awards the IXAS Dale Sayers Young Scientist Award to young scientists who made an outstanding contribution in the XAFS field. Dr. Carolin Schmitz-Antoniak from the group of  Prof. Dr. Heiko Wende recieved the prize during the 15th International Conference on X-ray Absorption Fine Structure (XAFS XV) in Peking for her work on the structure and magnetism of nanoscale systems. The prize is awarded in honour of Dale Sayers, one of the pioneers in modern x-ray spectroscopy for investigations of the local structure. Besides the certificate, Dr. Carolin Schmitz-Antoniak recieved 500 Dollars and a chinese tea set.

Dr. Bernhard Krumme

24.07.12 Bernhard Krumme

recieved his PhD on "Einfluss von Unordnung und Grenzflächen auf elektronische und magnetische Eigenschaften von Heusler-Systemen".

The thesis is available via the publications server of the university.

-> Bernhard's thesis on DuEPublico

FePt - scheme

14.11.11 Ultrahard nanomagnets

Scientists of the groups of Prof. Wende, Prof. Farle, and Prof. Entel published some of their recent work in “Nature Communications”.

Nanomagnets have become ubiquitous: in medicine applications as well as for data storage. Therefore they have to be sometimes strong, sometimes weaker. Members of the groups of Prof. Dr. Heiko Wende, Prof. Dr. Michael Farle, and Prof. Dr. Peter Entel investigated how to tailor the properties of such tiny magnets and published the results just recently.

more aboutUltrahard nano magnets” (German)

external information on “Ultrahard nano magnets”

Schematic of the magnetic coupling

06.05.10 Experiment of the month

How to beat the 75 year old Slater-Pauling limit?

Magnetic materials with a large saturation magnetic moment are used in various applications, such as write heads in computer hard disks, electromagnetic motors, generators, and transformers. Improved and more efficient materials are continuously sought after, but, for the last 75 years, the largest room temperature saturation moment (2.45 µB per atom), as described by the maximum of the Slater-Pauling curve, has been provided by an Fe-Co alloy. Rare earth metals have a larger magnetic moment, however they are not ferromagnetically ordered at room temperature. By combining ferromagnets like Fe with a rare earth element the ordering temperature is enhanced by the magnetic coupling to Fe. Unfortunately the coupling between such metals is antiferromagnetic which in turn reduces the net magnetization. In a joint work of the group of Prof. Wende and the theory group of O. Eriksson (Uppsala) this limitation was overcome by inserting an interlayer of Cr between the ferromagnet and the rare earth metal.

more aboutExperiment of the month” (German)

external link to the published paper.