New paper on

It has been known for over two decades that it is possible to manipulate magnetic order using femtosecond laser pulses. Many groups have demonstrated that single laser pulses can demagnetise a magnet on the picosecond time-scale, with a subsequent recovery of the order proceeding as the sample cools. Such measurements are routinely made these days using a pump-probe setup and detecting a change in the magnetic order through the Kerr effect. However, the pump beam is often micrometres across, hence what is measured is a spatial average. Just how the magnetic structure changes on the nanometre length-scale has, until now, not been well understood.

In a recent article in Nature Communications, in collaboration with several groups across the world, we have recently demonstrated how these magnetic structures vary across the nano-metre to micrometre length-scale and from the femto-second to nano-second time-scale. We have found “evidence of a universal rapid magnetic order recovery in ferrimagnets with perpendicular magnetic anisotropy via nonlinear magnon processes. We identify magnon localisation and coalescence processes, whereby localised magnetic textures nucleate and subsequently interact and grow in accordance with a power law formalism”.

This has been very well explained in this article on the University of Colorado Boulder’s website. The article is open access and hence free for anyone to download and read.

Fallot and Hocart 1939 FeRh Paper

I started looking at FeRh back in 2015 with Gino Hrkac in Exeter and Tom Thomson’s group in Manchester. This interesting material undergoes a change in its magnetic state from antiferromagnetic to ferromagnetic upon changing temperature (other stimuli are also possible). One of the original papers was by Fallot and Hocart and is regularly cited as such in the literature. However, I found that whilst it was well cited, I could not find a copy of the paper. It was often cited as – M. Fallot and R. Horcart, Rev. Sci. 77, 498 (1939). I tried for a while to find out which journal Rev. Sci. was by googling journal abbreviations (e.g. here) but to no avail.

Cover page for volume 77 and page 498 showing the first part of the article by Fallot and Hocart’s on FeRh.
Source gallica.bnf.fr / Bibliothèque nationale de France

Eventually, I tracked down the journal, which turned out to be “La Revue Scientifique”, which is a historic French journal founded in 1838 and, interestingly, also known as “La Revue Rose” due to the colour of its cover and in opposition to “La Revue Blue” (the nickname of “La Revue Politique et littéraire”. The particular edition (volume 77) from January 1939 has been scanned and can be found at the following link.

 

New COST Action on Ultrafast opto-magneto-electronics

The European Union have recently announced a new COST action entitled “Ultrafast opto-magneto-electronics for non-dissipative information technology” (MAGNETOFON). COST actions are networking instruments for researchers, engineers and scholars to cooperate and coordinate nationally funded research activities allowing researchers to develop ideas in a given area. This particular action aims at brining together researchers across Europe working in the areas of ultrafast spin dynamics, spintronics, magnonics, photonics and advanced spectroscopy. Proposed by Andrei Kirilyuk at Radbound University and was supported by researchers across 8 EU member states and 3 near neighbours. The details of the committee members representing the interests of the member countries is here.

The aim of the action is to initiate breakthroughs in the field of low-dissipative opto-magnetism by encouraging networking and training a new generation of scientists working in these fields. COST provides funding for networking activities, such as short term scientific missions, organising conferences, meetings and training schools.

More information is available at the COST website for MAGNETOFON – http://www.cost.eu/COST_Actions/ca/CA17123