HZB Newsroom

A team at HZB has investigated a new, simple method at BESSY II that can be used to create stable radial magnetic vortices in magnetic thin films.

New states of order can arise in quantum magnetic materials under magnetic fields. An international team has now gained new insights into these special states of matter through experiments at the Berlin neutron source BER II and its High-Field Magnet. BER II served science until the end of 2019 and has since been shut down. Results from data at BER II are still being published.

The travelling salesman problem is considered a prime example of a combinatorial optimisation problem. Now a Berlin team led by theoretical physicist Prof. Dr. Jens Eisert of Freie Universität Berlin and HZB has shown that a certain class of such problems can actually be solved better and much faster with quantum computers than with conventional methods.

Hafnium oxide thin films are a fascinating class of materials with robust ferroelectric properties in the nanometre range. While their ferroelectric behaviour is extensively studied, results on piezoelectric effects have so far remained mysterious. A new study now shows that the piezoelectricity in ferroelectric Hf_0.5Zr_0.5O₂ thin films can be dynamically changed by electric field cycling. Another ground-breaking result is a possible occurrence of an intrinsic non-piezoelectric ferroelectric compound. These unconventional features in hafnia offer new options for use in microelectronics and information technology.

A team at HZB has developed a new measurement method that, for the first time, accurately detects tiny temperature differences in the range of 100 microkelvin in the thermal Hall effect. Previously, these temperature differences could not be measured quantitatively due to thermal noise. Using the well-known terbium titanate as an example, the team demonstrated that the method delivers highly reliable results. The thermal Hall effect provides information about coherent multi-particle states in quantum materials, based on their interaction with lattice vibrations (phonons).

Magnetic skyrmions are tiny vortices of magnetic spin textures. In principle, materials with skyrmions could be used as spintronic devices, for example as very fast and energy-efficient data storage devices. But at the moment it is still difficult to control and manipulate skyrmions at room temperature. A new study at BESSY II analyses the formation of skyrmions in ferrimagnetic thin films of dysprosium and cobalt in real time and with high spatial resolution. This is an important step towards characterising suitable materials with skyrmions more precisely in the future.