Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chain instead of zigzag: RUB physicists let magnetic dipoles interact on the nanoscale

16.05.2013
Of great technical interest for future hard disk drives

Physicists at the Ruhr-Universität Bochum (RUB) have found out how tiny islands of magnetic material align themselves when sorted on a regular lattice - by measurements at BESSY II. Contrary to expectations, the north and south poles of the magnetic islands did not arrange themselves in a zigzag pattern, but in chains.

“The understanding of the driving interactions is of great technological interest for future hard disk drives, which are composed of small magnetic islands”, says Prof. Dr. Hartmut Zabel of the Chair of Experimental Physics / Solid State Physics at the RUB. Together with colleagues from the Helmholtz-Zentrum in Berlin, Bochum’s researchers report in the journal “Physical Review Letters”.

Complete chaos in the normal state

Many atoms behave like compass needles, that is, like little magnetic dipoles with a north and a south pole. If you put them close together in a crystal, all the dipoles should align themselves to each other, making the material magnetic. However, this is not the case. A magnetic material is only created when specific quantum mechanical forces are at work. Normally, the forces between the atomic dipoles are by far too weak to cause magnetic order. Moreover, even at low temperatures, the thermal energy causes so much movement of the dipoles that complete chaos is the result. “However, the fundamental question remains of how magnetic dipoles would align themselves if the force between them was big enough”, Prof. Zabel explains the research project.

Square lattice of magnetic islands

To investigate this, the researchers used lithographic methods to cut circular islands of a mere 150 nanometers in diameter from a thin magnetic layer. They arranged these in a regular square lattice. Each island contained about a million atomic dipoles. The forces between two islands were thus stronger by a factor of a million than that between two single atoms. If you leave these dipoles to their own resources, at low temperatures you can observe the arrangement that results exclusively from the interaction between the dipoles. They assume the most favourable pattern in terms of energy, the so-called ground state. The islands serve as a model for the behaviour of atomic dipoles.

Magnetic microscopy

The electron synchrotron BESSY II at the Helmholtz-Zentrum in Berlin is home to a special microscope, the photon emission electron microscope, with which the RUB physicists made the arrangement of the magnetic dipole islands visible. Using circularly polarised synchrotron light (X-ray photons), the photons stimulate specific electrons. These provide information on the orientation of the dipoles in the islands. The experiments were carried out at low temperatures so that the thermal movement could not interfere with the orientation of the dipoles.

Dipoles arrange themselves in chains

The magnetic dipoles formed chains, i.e. the north pole of one island pointed to the south pole of the next island. “This result was surprising”, says Zabel. In the lattice, each dipole island has four neighbours to which it could align itself. You cannot tell in advance in which direction the north pole will ultimately point. “In fact, you would expect a zigzag arrangement”, says the Bochum physicist. Based on the chain pattern observed in the experiment, the researchers showed that higher order interactions determine how the magnetisation was oriented. Not only dipolar, but also quadrupolar and octopolar interactions play a role. This means that a magnetic island exerts forces on four or eight neighbours at the same time.

Magnetic islands in the hard drives of the future

In future, hard disks will be made up of tiny magnetic islands (bit pattern). Each magnetic island will form a storage unit which can represent the bit states “0” and “1” - encoded through the orientation of the dipole. For a functioning computer, you need a configuration in which the dipole islands interact as little as possible and can thus assume the states “0” and “1”independently of each other. For the technical application, a precise understanding of the driving interactions between magnetic islands is therefore crucial.

Funding

The German Research Foundation (DFG) supported the work in Bochum within the Collaborative Research Centre (SFB) 491 „Magnetic hetero-structures: spin structures and spin transport“; BESSY II at the Helmholtz-Zentrum Berlin is supported by the Federal Ministry of Education and Research (BMBF).

Bibliographic record

M. Ewerlin, D. Demirbas, F. Brüssing, O. Petracic, A.A. Ünal, S. Valencia, F. Kronast, H. Zabel (2013): Magnetic Dipole and Higher Pole Interaction on a Square Lattice, Physical Review Letters, DOI: 10.1103/PhysRevLett.110.177209

Figures online

Two images related to this press release can be found online at:
http://aktuell.ruhr-uni-bochum.de/pm2013/pm00144.html.en

Further information

Prof. Dr. Hartmut Zabel, Chair of Experimental Physics / Solid State Physics at the Ruhr-Universität, 44780 Bochum, Germany, Tel. +49/234/32-23649, E-mail: hartmut.zabel@rub.de

Editor: Dr. Julia Weiler

Dr. Josef König | idw
Further information:
http://www.ruhr-uni-bochum.de

More articles from Physics and Astronomy:

nachricht APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie

nachricht First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science

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: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>