IOP Postgraduate Magnetic Techniques Workshop


The 2013 “Postgraduate Magnetic Techniques Workshop” organised by the Insitute of Physics is taking place today. It is a workshop to provide introductory training in key experimental and theoretical techniques used in magnetic research, aimed at new postgraduate students and research fellows new to magnetic research. My talk will be on the atomistic spin dynamics model and how it can be used to describe magnetization dynamics in the femtosecond regime. I will focus on how the model is constructed and how it is being used to compare to experimental observations. The talk will be available on the conference presentations page.

Installing Rasmol on OS X (10.8.5)

I am used to using rasmol for quick viewing of atomic positions. For example to check that my system generation creates an fcc structure with two layers, one with Nickel and one Iron:

Screen Shot 2013-12-03 at 18.35.58

To avoid compiling the binary from source there are a number of pre-compliled binaries for different platforms available here. My aim was to install a working version to /usr/local/ on the mac filesystem. I went for a filetype that had a name like:


This should run on a mac with an intel chip (I hope). Download this and untar it. Once it has been untarred upen up a terminal and move into the newly unpacked directory. In the terminal you can do this by downloading the file to, for example, /Users/username/Downloads, where you put your username in <username>. Then change to that directory and untar the file.

This made a directory called RasMol_2_7_5_i386_OSX_21Jul09, change to that directory.

install to /usr/local/ by running the file with the path prefix as /usr/local

It will ask you if this is where you want to put the bin and lib directories. Hit ‘y’ twice and enter. From a terminal you should be able to call rasmol now as /usr/local/bin should be in the executable path.

Microscopic Explanation of Thermally Induced Magnetization Switching

Microscopic explanation of thermally induced magnetisation switching

Since the discovery of a purely thermally induced magnetisation switching (TIMS) in GdFeCo, there has been much effort to identify the cause of this unexpected phenomenon. While several works have studied the macroscopic relaxation behaviour (Mentink et al., Phys. Rev. Lett. 108, 057202 (2012).  Atxitia et al., Phys. Rev. B 87, 224417 (2013)), there has been little headway made in finding the material origins of the switching. In our new work “Two-magnon bound state causes ultrafast thermally induced magnetisation switching” published in the open access journal Scientific Reports we have found, through simulation and described with a combination of theoretical approaches, that the switching is caused by angular momentum transfer from a two magnon bound state which exists in this class of ferrimagnetic materials. Specifically, within GdFeCo we have shown that the amorphous properties of the material affect the switching behaviour because the antiferromagnetic interactions which couple the rare-earth and transition metal species have a large effect only at the interfaces of Gd clusters within the FeCo background. Our work provides a new insight into the switching which is induced by femtosecond laser pulses and gives new directions for experimentalists to focus their research.

Thanks to Joe Barker for creating this blog post.