Tiny, Tailored Magnets - CeNIDE Researchers Publish in “Nature Communications”
Synchrotron Radiation Source BESSY II
Nanomagnets are used in many places nowadays, from medicine to data storage. Sometimes they have to be strong and and sometimes they have to be weak. Researchers from the Center for Nanointegration (CeNIDE) at University of Duisburg-Essen (UDE) have found out just how to produce these tiny magnets with highly specific properties, and have published their results.
Nanomagnets, some ten thousand times smaller than the thickness of a sheet of paper, make advanced data storage possible, serve as contrast media in MRI tests and are used for hyperthermic treatment in cancer patients. These are but a few examples of their applications, yet it is clear how highly demanded nanomagnets are for so many applications and with so many different properties. In computer memory, for example, nanomagnets have to remain in fixed alignment if they are to store data for any length of time. Were they ever to change their magnetic alignment spontaneously, then the stored information would be lost. Hyperthermic treatment of cancer patients, by contrast, requires nanomagnets that can switch polarity very easily. This treatment involves introducing the teensy particles directly into the tumour and then rapidly reversing their magnetization using external magnetic fields. The nanomagnets thereby produce heat that locally destroys the surrounding cancer cells.
Working together, the workgroups of experimental physicist Prof. Heiko Wende and theoretical physicist Prof. Peter Entel have now defined concrete rules by which to precisely determine the properties of nanomagnets in their production. On the experimental front, Prof. Wende and his group coated the nanoparticles in various metals and then measured these metals’ effects on the magnetic properties of the particles inside. To obtain the most meaningful and detailed data, the researchers used a measuring instrument of a wholly different scale: inside a ring system 240 metres long, BESSY II of Helmholtz Zentrum Berlin accelerates electrons to near light speed. The high brilliancy X-rays they subsequently produce yield information on the magnetic properties of the sample. Dr. Carolin Antoniak spent several sleepless nights working the switch panels of the large facility: “But it definitely paid off,” the physicist emphasizes. “Only here were we able to perform our measurements to such detail and to distinguish between various types of magnetization.” Meanwhile, on the theoretical front, Dr. Markus Gruner from the workgroup of Prof. Entel computed the influence of the different coating metals on every single atom inside a nanomagnet. To perform these complex calculations, the theoretical physicist used Europe’s largest academic research computer JUGENE at the Jülich Research Centre, which can perform up to a quadrillion computations a second. “You’re standing there in a hall next to 72 huge cabinets that house the computer,” Gruner says with awe. “We had to compute for several weeks on over a thousand processors simultaneously until we had certainty. You can only do that sort of thing on JUGENE.”
Both approaches – experimental and theoretical – complement each other ideally: While the theoretical calculation is extremely precise, it is still based on assumptions. Assumptions that must be confirmed by experiment. Now, the research cooperation can predict which properties can be achieved with which metal coating. Also, characteristics of hitherto uncreated types of nanomagnets can now be reliably calculated based on the data obtained. That means nanomagnets can already be tailored to the desired properties during their production. This makes life enormously easier for all kinds of users.
“We have decided to coat the nanomagnets with organic materials in future,” explains Wende. “Then it may well be possible to modify the properties afterwards using external influences such as light, for example.”
Contact & Information:
CeNIDE – Center for NanointegrationDuisburg-Essen
Universität Duisburg-Essen
Frau Birte Vierjahn
Public Relations
Forsthausweg 2
47057 Duisburg
Fon: +49.203.379.1456
Fax: +49.203.379.1895
E-Mail: birte.vierjahn@uni-due.de
www.cenide.de
Dr. Carolin Antoniak
Experimentalphysik - AG Wende
Universität Duisburg-Essen
Gebäude MD
Lotharstr. 1
47057 Duisburg
Fon: +49.203.379.2389
Fax: +49.203.379.3601
E-Mail: carolin.antoniak@uni-due.de
http://www.uni-due.de/physik/wende/
- BESSY II: New sample environment allows glimpse into thermocatalytic processesA novel measurement cell allows, for the first time, soft and hard X-ray investigations under high pressures of up to 20 bar and temperatures of up to 400°C. This provides new insights into thermocatalytic processes, such as the Fischer-Tropsch synthesis for producing synthetic fuels. The development of the measurement cell is considered a significant achievement within the Care-O-Sene project.
- Magnetic imaging: Micro-flowers increase the local magnetic fieldMaterials with magnetic nanostructures have many potential applications such as in spintronics. To explore such materials, nanoscale magnetic-sensitive imaging techniques are very useful, but up to now only weak magnetic fields could be applied during the imaging process. Now an international collaboration led by Dr. Sergio Valencia, HZB, has developed an approach that overcomes this limitation. The team designed tiny magnetic flux concentrators (MFCs), into which the sample is placed. The geometry of the MFCs resembles a flower with a number of petals which focus the applied magnetic field into its center. This greatly expands the magnetic field range available during imaging, and so the range of magnetic systems that can be investigated. The micro-flowers, enhancing magnetic fields locally, can find application in different nanometric magnetic microscopy techniques.
- Disorder creates new properties in compound semiconductorsAn international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appear isotropic, as expected for a cubic crystal. In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening up new options for targeted 'disorder engineering' in optoelectronic and photocatalytic devices.