Ultrafast magnets that can learn

May 2019

The power consumption of information storage and processing around the world is increasing. This creates a high demand for new technologies that could lead to more energy-efficient computers. The human brain can solve certain problems like pattern recognition with only 20W, while a supercomputer would need 10MW for the same task. Therefore, many researchers world-wide now try to realize brain-inspired computing principle in materials. In a new study, we experimentally demonstrate that it is possible to create artificial synapses by using ultrashort laser pulses in combination with materials that are nowadays used in magnetic hard disc drives. Moreover, we show that by combining such synapses, supervised learning can be achieved. These results suggest that there is high potential for realizing artificial neural networks using optically controlled magnetization in technologically relevant materials, which can learn not only fast but also energy-efficient.


Picture by Ashim Chakravarty. Press release from Radboud University (English, Dutch). Further coverage by PhysOrg and EngineersOnline


Review article:

Manipulating magnetism by ultrafast control of the exchange interaction

October 2017

In recent years, the optical control of exchange interactions has emerged as an exciting new direction in the study of the ultrafast optical control of magnetic order. In this article, we review recent theoretical works on antiferromagnetic systems, devoted to (i) simulating the ultrafast control of exchange interactions, (ii) modeling the strongly nonequilibrium response of the magnetic order and (iii) the relation with relevant experimental works developed in parallel. In addition to the excitation of spin precession, we discuss examples of rapid cooling and the control of ultrafast coherent longitudinal spin dynamics in response to femtosecond optically induced perturbations of exchange interactions. These elucidate the potential for exploiting the control of exchange interactions to find new scenarios for both faster and more energy-efficient manipulation of magnetism. 


PhD position:

Condensed matter physics inspired by the brain


This project is part of a new research direction that we aim to develop based on our extensive experience for multi-scale modelling op laser-induced nonequilibrium dynamics of magnetism. On the one hand, it aims to predict how solid state magnetic materials can be dynamically manipulated to exhibit learning behavior, a property usually associated with the brain. On the other hand, it aims to exploit neural principles to describe the dynamics of quantum spin systems more efficiently on classical computers using concepts from machine learning. Basing on methodologies from condensed matter theory, both approaches will be developed in close connection with theoretical neuroscience and experimental condensed matter physicists, ultimately aimed at enabling information processing concepts that operate at orders of magnitude lower energy cost than existing technology.


New route for switching magnets using light

September 2015

In a publication in Nature Communications, we have shown experimentally that a strong pulse of light can have a direct effect on the strong quantum mechanical 'exchange interaction'. The results are supported by theoretical calculations and suggest that reversing the poles of magnets must be possible without using heating or a magnetic field.


Picture by D.V. Afanasiev. Press release available from Radboud University.


Turning back time and more efficient switching of magnets with light

March 2015
In a publication in Nature Communications, we have predicted that the interactions that govern the collective behavior of microscopically small magnets (spins) in magnetic materials can be controlled with light both reversibly and almost instantaneously. This provides a theoretical basis for more efficient magnetic recording technology. Moreover, the finding implies the highly counter-intuitive consequence that the magnetic dynamics can effectively run backwards in time under the influence of a sufficiently strong time-periodic laser field. 

Picture © MPSD J.M. Harms. Press releases available from Max Planck Institute for the Structure and Dynamics of Matter (English) and Radboud University (Dutch).


Manipulating magnetic forces with light

July 2014

The magnetic forces in materials like iron can be rapidly manipulated with light. We have demonstrated this theoretically in a publication in Physical Review Letters by combining two recent major methodological developments. Rapid and effective manipulation of magnetic states is of high fundamental and technological value. For example, it could be used for the development of faster hard disks.


Press releases available from CFEL and NWO.


Magnets are chaotic – and fast – at the very smallest scale

January 2013

Using a new type of camera that makes extremely fast snapshots with an extremely high resolution, it is now possible to observe the behaviour of magnetic materials at the nanoscale. This behaviour is more chaotic than previously thought, as we reported with an international team of scientists in Nature Materials.

Press release available from Radboud University.


PhD thesis

Magnetism on the timescale of the exchange interaction - explanations and predictions
October 2012

You will find my PhD thesis here.



Scientists 'record' magnetic breakthrough

February 2012

With an international team of scientists we have demonstrated a revolutionary new way of magnetic recording without the use of a magnetic field. Instead we could record information using only an ultra short heat pulse – a previously unimaginable scenario. As reported in Nature Communications, this discovery may not only allow information to be processed hundreds of times faster than by current hard drive technology, but it can be more energy-efficient too.


Press release available from the University of York.


Breakthrough in the understanding of magnetism

January 2012

A new theory on how magnetism actually works on short time scales opens up possibilities for whole new experiments to rapidly store data. The theory is published in Physical Review Letters. We are able to explain recent highly counter-intuitive experimental results on laser-induced magnetic switching and provide predictions for new and revolutionary ways of controlling magnetism.


Press release available from Radboud University (in Dutch).