Prof. Johan Åkerman's group at The Physics Department, University of Gothenburg (GU) announces four post-doctoral positions within projects funded by the European Research Council (ERC), the Swedish Research Council (VR) and the Knut & Alice Wallenberg Foundation (KAW). The Åkerman group continuous to show a very active and internationally visible research presence with the goal to uncover novel magnetic, spintronic and magnonic phenomena for utilization in nano-electronic applications at microwave and THz frequencies. For this purpose we develop novel frequency and time-resolved magnetodynamic tools based both in the electrical and optical domain and collaborate with local and international groups on THz electronics and Nanoplasmonics.

Please note that all applications must be made online using the GU application system. More information about the positions can be found here.

MML (International Symposium on Metallic Multilayers) is one of the best thin film magnetism conferences out there. The 8th version of it was no exception. Randy Dumas and Johan Åkerman attended and presented two posters [1,2] and an invited talk [3]. The next MML 2016 will be held in Uppsala, Sweden! Expect to see the entire Åkerman Group to be attending, if allowed.



[1]  "A non-volatile spintronic memory element with a continuum of resistance states", Y. Fang, R. Dumas, T. Anh Nguyen, S. Mohseni, S. Chung, C. Miller, J. Åkerman, Poster P-71
[2] "Spin wave mode coexistence in nanocontact spin torque oscillators", R. Dumas, E. Iacocca, S. Bonetti, S. Sani, M. Mohseni, A. Eklund, J. Persson, O. Heinonen, J. Åkerman, Poster P-124
[3] "Magnetic droplet solitons in nano-contact spin-torque oscillators with perpendicular magnetic anisotropy", J. Åkerman, M. Mohseni, S. Sani, J. Persson, A. Nguyen, S. Chung, Y. Pogoryelov, P. Muduli, E. Iacocca, A. Eklund, R. Dumas, S. Bonetti, A. Deac, M. Hoefer, Invited Talk We-1

PhD student Yeyu Fang is one of twelve Chinese graduate students in Sweden awarded the Chinese Government Scholarship 2012 for outstanding self-financed students studying abroad.

Yeyu received a diploma at a ceremony at the Chinese Embassy in Stockholm on Friday, May 17. Prof. Johan Åkerman held a short speech as representative of the supervisors of the 12 students.

Big congrats from everybody in the group!

Anh Nguyen, Randy Dumas and Johan Åkerman have published a paper in Phys. Rev. B on Brillouin Light Scattering measurements of fundamental spin wave modes in tilted exchange springs [1]. These results are part of an ongoing collaboration with the University of Perugia, Italy, and also involved collaborators from Florence, Italy, and NIST Gaithersburg, USA.

[1] S. Tacchi, T. N. Anh Nguyen, G. Carlotti, G. Gubbiotti, M. Madami, R. K. Dumas, J. W. Lau, Johan Åkerman, A. Rettori, and M. G. Pini, "Spin wave excitations in exchange-coupled [Co/Pd]-NiFe films with tunable tilting of the magnetization", Phys. Rev. B 87, 144426 (2013)

This YouTube clip is from SSF's (The Swedish Foundation for Strategic Research) YouTube Channel where they show an interview of Johan Åkerman and Sohrab Redjai Sani recently aired on TV4 Science (Swedish: TV4 Vetenskap). Half of the clip is in Swedish but if you jump to about 3:35 grad student Sohrab explains some of the lithography steps in English.

Drops are natural objects in systems with attractive forces. Water drops are e.g. formed from the attractive polar interaction between the H atoms in one H2O molecule and the O atom in another.  In ultrathin magnetic films the so-called perpendicular magnetic anisotropy (PMA) can create an attraction between spin wave excitations (magnons) and if a sufficient number of magnons are present in a region (analogous to a sufficient number of water molecules) they can condense into a magnon drop where all spins in the drop precess in-phase on a single magnon frequency.

Magnon drops were predicted theoretically by Ivanov and Kosevich over 35 years ago [Zh. Eksp. Teor. Fiz. 72, 2000 (1977)]. More recently, Hoefer, Silva and Keller demonstrated analytically and numerically that nano-contact spin torque oscillators (NC-STOs) with PMA free layers should be able to nucleate and sustain the dissipative (= lossy and actively driven) analogue of magnon drops; they called this new potential soliton object a magnetic droplet [Phys. Rev. B 82, 054432 (2010)].

In this work, we present the first experimental demonstration of magnetic droplets. Our devices consist of NC-STOs with a Co fixed layer and a [Co/Ni] multilayer free layer. The creation of a magnetic droplet is experimentally observed as a dramatic 10 GHz drop in the measured microwave frequency, accompanied with a sharp increase in the device resistance. The droplet displays a wide range of additional magnetodynamic phenomena, experimentally observed as a number of sidebands at different frequencies. Our work both brings closure to a long-standing theoretical prediction and provides the nanomagnetic and spintronic community with a novel dynamic nanomagnetic object, which joins the magnetic domain wall and magnetic vortex with similar potential for rich science.

S. M. Mohseni, S. R. Sani, J. Persson, T. N. Anh Nguyen, S. Chung, Ye. Pogoryelov, P. K. Muduli, E. Iacocca, A. Eklund, R. K. Dumas, S. Bonetti, A. Deac, M. A. Hoefer, and J. Åkerman, Spin Torque–Generated Magnetic Droplet Solitons, Science 339, 1295 (2013).