Magnetic transitions using ions

Dr. Rantej Bali

Projects

• Microscopic understanding of disorder induced ferromagnetism in B2-alloy thin films II (DFG funded)

Topics

1. Structure-property relationships in B2 alloys Disorder in B2 alloys such as Fe-Al, Fe-Rh and Fe-V leads to a drastic increase of the magnetization. The atomic arrangement on the left is that of an ordered B2 alloy. Ion-irradiation can be used to cause disorder, shown by the arrows on the right, and increase the magnetization at the nanoscale. We explore this phenomena using ion-beams combined with a variety of magnetometric and spectroscopic tools. (more info...)

2. Magnetic patterning using ions Disorder induced ferromagnetism can be deployed for patterning ferromagnetic nanostructures embedded within non-ferromagnetic surroundings. Shown here is a TEM holographic image of magnetic field lines emerging from two 500 nm wide ferromagnetic stripes. The pattern is comparable to that of bar magnets separated by a few mm spacing. Here, we also observe features that are less than 100 nm in size. (more info...)

3. Magnetism and transport in nanostructures Periodic magnetic structures show intriguing magnetization reversal, transport and dynamic properties. For examples,  we have shown that confined antidot structures (above) can possess multiple magnetization configurations. These configruations may translate into programmable spin-wave and magneto-transport properties. (more info...)

External Collaborators:

• Prof Heiko Wende, University Duisburg-Essen
• Dr Florian Kronast, Helmholtz-Zentrum Berlin
• Dr Markus Gruner, University Duisburg-Essen
• Prof Adekunle Adeyeye, National University of Singapore
• Prof Jürgen Bauch, Technische Universität Dresden
• Dr Richard Boucher, Technische Universität Dresden
  
• Prof Mikhail Kostylev, University of Western Australia
• Prof Andrzej Maziewski, University of Białystok
• Dr Plamen Stamenov & Kiril Borisov, Trinity College Dublin
• Prof Tomayasu Taniyama, Tokyo Institute of Technology
• Dr Sabine Wurmehl, IFW Dresden
• Prof Björgvin Hjörvarrsson, Uppsala University

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Selected Publications:

[1] Focused Helium and Neon Ion Beam Modification of High-T C Superconductors and Magnetic Materials, Shane A Cybart, Rantej Bali, Gregor Hlawacek, Falk Röder, Jürgen Fassbender, Book Chapter, Helium Ion Microscopy 2016 (Link).

[2] Programmability of Co-antidot lattices of optimized geometry, Tobias Schneider, Manuel Langer, Julia Alekhina, Ewa Kowalska, Antje Oelschlägel, Anna Semisalova, Andreas Neudert, Kilian Lenz, Kay Potzger, Mikhail P. Kostylev, Jürgen Fassbender, Adekunle O. Adeyeye, Jürgen Lindner & Rantej Bali, Scientific Reports 2016 (Link).

[3] Direct Depth- and Lateral- Imaging of Nanoscale Magnets Generated by Ion Impact, Falk Röder, Gregor Hlawacek, Sebastian Wintz, René Hübner, Lothar Bischoff, Hannes Lichte, Kay Potzger, Jürgen Lindner, Jürgen Fassbender & Rantej Bali, Scientific Reports 2015, (Link).

[4] Tuning the antiferromagnetic to ferromagnetic phase transition in FeRh thin films by means of low-energy/low fluence ion irradiation, A Heidarian, R Bali, J Grenzer, RA Wilhelm, R Heller, O Yildirim, J Lindner, K Potzger, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2015, (Link)

[5] Printing Nearly-Discrete Magnetic Patterns Using Chemical Disorder Induced Ferromagnetism, Rantej Bali, Sebastian Wintz, Falk Meutzner, René Hübner, Richard Boucher, Ahmet A. Ünal, Sergio Valencia, Andreas Neudert, Kay Potzger, Jürgen Bauch, Florian Kronast, Stefan Facsko, Jürgen Lindner, and Jürgen Fassbender, Nano Letters 2014, (Link).