Magnetism

Whilst magnetic and correlated electron materials are centrally important to modern information and energy technologies, they are far from being fully understood. Fundamental scientific questions remain about their behaviour, and their detailed understanding promises revolutionary new foundations for technology. The special properties of light and microwaves provide unrivalled opportunities to examine the electronic and magnetic structure and function of these materials. The in-house research activities aim to realize this potential while concentrating on topics where the probes can make uniquely important contributions.

These include:

1. Functional Materials for Magnonics and Spintronics

• Investigation of phase-change magnonics/magnonics based on ion beam modified materials:
  Disorder-induced ferromagnetism in otherwise chemically ordered binary metal alloys, like FeAl, offers the possibility for nanoscale magnetic patterning by means of ion beam related lithography. Such patterning will allow the investigation of magnetization dynamics in individual structures or coupled arrays of sub-20 nm dots, i.e. by making use of a He/Ne-ion microscope or single ion implantation at predefined locations with nm resolution.
• Tailoring of magnetic materials by ion doping:
  Investigation of ion-induced effects on magnetic phenomena like saturation, anisotropy, magnetic relaxation channels, spin-Hall angle, or spin-pumping properties. The combination with patterning techniques allows for the creation of hybrid magnetic materials with tailored properties.
• Towards single electron spintronics:
  Contacting individual ferromagnetic nano­particles by using self-assembly techniques and top down approaches in order to demonstrate magneto-coulomb effects.

2. Magnetization dynamics: Driven and ultrafast transient states

• Control of magnetic relaxation ‒ Individual nanostructures (building blocks) towards networks (mesoscopic structures):
  The possibility to disentangle and thus understand magnetic damping contributions is of importance to tailor damping e.g. by local magnetic patterning. Employing microresonators or alternative detection schemes (optical, electrical) to investigate ferromagnets at the nanoscale will reveal understanding of mechanisms governing magnetic relaxation at small dimensions.
• Spin-torque oscillators – moving the frequency output towards THz regime:
  To achieve a breakthrough into the sub-THz and THz range, we will investigate the potential of using the large intrinsic fields of novel classes of materials, like ultrahigh anisotropy ferro- and ferrimagnets, or strong exchange interaction antiferromagnets to be exploited for increasig the resonance frequency by at least an order of magnitude. Such effects in single nanoscale devices may enable wireless THz communication. 
• Mutual interaction between spin-waves/spin-currents and plasmons:
  Recent developments in spintronics as well as photonics show the potential of magnonics to become a powerful “bridge technology” closing the gap on the time- and length-scale between charge and photon physics. Newly discovered effects such as the direct and inverse spin Hall-effects as well as spin-pumping and spin-transfer torque, on the one side, allow for the mutual conversion of spin-waves into spin currents and vice versa. Information processing based on spin-waves is reprogrammable, which means that logic operations in magnonic circuits can be adapted to specific problems.
• Studying the magnetodynamics of multilayer vortices and skyrmion spin textures
  with special emphasis on magnetoresistance, spin-torque, and predicted spin-wave emission effects. Experimentally, individual objects will be addressed by means of synchrotron based time resolved X-ray microscopy, since this is the only technique providing the necessary combination of elemental, temporal, and spatial resolution.

Groups:

• Interface Magnetism
• Magnetization Dynamics
• Magnonics (Emmy Noether Independent Junior Research Group)
• Intelligent Materials and Devices
• Magnetic Functional Materials