Spin transport is an innovative fields in magnetism over the last decade due to groundbreaking discoveries: magnetic-quantum size effects, giant tunnel magnetoresistance (giant TMR) and the interaction of spin-currents within a magnetic nanometer sized pillar, the so called 'spin-transfer torque'.

Our aim is to bring the understanding of femtosecond spectroscopy and transport through magnetic nanostructures together. Our expertise lies in ultrafast dynamics and building nanostructure devices.

Dynamics on an ultrafast timescale determines the read write access time in future memory's. Our research explores the physics of ultrafast spin dynamics and spin manipulation with the help of femtosecond laser pump-probe experiments. The fundamental understanding of light-matter interaction on the femtosecond timescale allows an insight into the elementary spin relaxation in spin-electronic materials, such as half metals. Therewith we developed novel tools to characterize their spin polarization. Within shorter time scales it is possible to have access to spin waves at terahertz (THz) frequency. Their exploration is a key to ultrafast switching and spin-wave condensation in periodic confinements (magnonic crystals) and sets the foundations for novel magnonic logic devices and spin-wave based computing. Ultrafast spin dynamics projects are done in collaboration with Oksana Chubykalo-Fesenko (ICMM Madrid), Tobias Kampfrath (Fritz-Haber Institute Berlin) and Tiffany Santos (San Jose Research Center, HGST, a Western Digital Company).

The generation and detection of laser induced topological surface currents (spin-momentum locking) is the topic of a joint project. Spin polarized currents in topological insulators and their dynamics are investigated in the priority programme"Topological Insulators: Materials - Fundamental Properties - Devices“ (SPP 1666)" together withTobias Kampfrath (Fritz-Haber-Institute Berlin) and Christian Heiliger (Giessen University).  An international collaboration supported by the DAAD-PPP project with the Czech Republic in a joint project FemtomagTopo with Eva Schmoranzerova (Laboratory of Opto-Spintronics, Charles University Prague) started in March 2015.

We are member of the interdisziplinary centerfor Innovation Competence - Humoral Immune Reactions in Cardiovascular Diseases (ZIK-HIKE) funded by the BMBF in the second round. We develope nanostructures for cell-related applications that allow to define specific artifical boundaries for bio-nanomechnical systems. This research is carried out together with  Mihaela Delcea.

Which elementary processes determine the output signal and functionality of a magnetic transport device? They are the building blocks for magnetic random access memory (MRAM) based processors, owning non volatile information at system restart, and via the spin-transfer torque effect. We nanometer thick highly ordered oxide layers serve as an “electron spin filter”. Specially designed "soft semiconductors", novel organic materials open up new possibilities as "active" tunnel barriers. This is done in collaboration with Jagadeesh Moodera (MIT) and Swadhin Mandal (IISER Kolkata).

The investigation of spin polarized currents in magnetic nanostructures arising from thermal gradients is aim of the new priority programme "Spin Caloric Transport" 1538 aims to understand thermocurrents and voltages including the spin. Together with Andy Thomas (Bielefeld University) and Christian Heiliger (Giessen University) we investigate the effects of thermal currents in magnetic tunnel junctions within two projects. The research at the three universities is funded with more than a million Euro. This joint research resulted in the finding of the magneto-Seebeck effect that allows controlling energy conversion via the magnetization in magnetic tunnel junctions.

Selected publications:

Terahertz spin current pulses controlled by magnetic heterostructures

T. Kampfrath, M. Battiato, P. Maldonado, G. Eilers, J. Nötzold, S. Mährlein, V. Zbarskyy, F. Freimuth, Y. Mokrousov, S. Blügel, M. Wolf, I. Radu, P. M. Oppeneer, M. Münzenberg, Nature Nanotechnology 8, 256 (2013).

Interface-engineered templates for molecular spin memory devices

K. V. Raman, A. M. Kamerbeek, A. Mukherjee, N. Atodiresei, T. K. Sen, P. Lazić, V. Caciuc, R. Michel, D. Stalke, S. K. Mandal, S. Blügel, M. Münzenberg, J. S. Moodera, Nature 493, 509 (2013)

Seebeck effect in magnetic tunnel junctions

M. Walter, J. Walowski, V. Zbarsky, M. Münzenberg, M. Schäfers, D. Ebke, G. Reiss, A. Thomas, P. Peretzki, M. Seibt, J.S. Moodera, M. Czerner, M. Bachmann, C. Heiliger, Nature Materials 10, 742 (2011).

The building blocks of magnonics (review)

B. Lenk, H. Ulrichs, F. Garbs, M. Münzenberg, Physics Reports 507, 107 (2011).

Spin polarization in half metals probed by femtosecond spin excitation

G. Müller, J. Walowski, M. Djordjevic, G.-X. Miao, A. Gupta, A. V. Ramos, K. Gehrke, V. Moshnyaga, K. Samwer, J. Schmalhorst, A. Thomas, A. Hütten, G. Reiss, J. S. Moodera, M. Münzenberg, Nature Materials 8, 56 (2009).

Energy equilibration processes of electrons, magnons, and phonons at the femtosecond time scale

J. Walowski, G. Müller, M. Djordjevic, M. Münzenberg, M. Kläui, C. A. F. Vaz and J. A. C. Bland, Phys. Rev. Lett. 100, 246803 (2008).

Connecting the timescales in picosecond remagnetization experiments
M. Djordjevic, M. Münzenberg, Phys. Rev. B 75, 012404 (2007).

Selected invited talks (slides as .pdf):

Talk: Magneto-Seebeck effect
Workshop on charge and heat dynamics in nano-systems, Laboratoire Physique des Solides, Orsay, France, 10.-12.10.2011.

Talk: Photo-Magnonics
2nd Workshop on Magnonics, Recife, Brazil, 7.-10.8.2011.

Talk: Accessing microscopic dynamic processes using ultrafast lasers
International Workshop on Spin Dynamics in Nanomagnets, Dissipative versus Non-Dissipative Processes, Universität Duisburg-Essen, 18.10.-20.10.2010.