Today sees the publication of my latest article, published in Scientific Reports. This work involves the use of first principles methods and atomistic spin dynamics to study the magnetic properties of Fe/Ir/Fe sandwiches. Such magnetic systems with interfaces are extremely difficult to model accurately, but by using first and second principles models we have been able to obtain layer-by-layer equilibrium and dynamic properties, which are even trickier to determine experimentally.
By using the SIESTA code to structurally relax the interfaces (see schematic) of different Ir, the ground state atomic structure can be found. We then used the Budapest SKKR code to determine an extended Heisenberg Hamiltonian. This complex Hamiltonian has a complete lack of translational invariance perpendicular to the plane, essentially meaning that each Iron plane is in its own environment which interact differently with the others. Our spin dynamics results show that this has important consequences for the equilibrium magnetic properties, as well as the dynamics. We find that the spinwaves are stiffened with increasing temperature, which goes against the thermal effects that usually result in a decrease. This is due to the frustration arising from the exchange at the interface with Ir. Finally, our results reveal a plane-wise dependence of the demagnetisation process.
The work was done in collaboration with international groups including ICN2 (Barcelona), Budapest University of Technology and the Universities of Exeter and York. The work is Open Access meaning that it is free for all to view (see this link). This was made possible due to the Sheffield Hallam University Open Access Fund. I would also like to thank Eddy Verbaan and the Library Research Support Team for their help in obtaining funding to make this article Open Access.
The Materials and Engineering Research Institute (MERI) at Sheffield Hallam University is funding 2 Graduate Teaching Assistant PhD studentships on any topic in materials and engineering, physics and mathematics. This is a competitive process, whereby applications from students are made with the support of an academic at Sheffield Hallam. A short proposal of the work during the PhD is required and can be done in collaboration with the academic. Potential projects in the areas of computational magnetism are:
Ultrafast spin dynamics in systems with emergent phenomena – involving a multiscale approach, combining first and second principles modeling.
Low energy control of magnetism in complex magnetic materials – using a range of approaches to simulate the dynamics of advanced functional materials to find new materials and routes towards low energy devices.
Potential projects are not limited to those described above. If you have a specific project in mind or if you require more information on these potential projects, please get in touch by email.
The deadline for applications is 1st Febrary 2018, see this link for more details on the application process and eligibility criteria.
Today, our first year undergraduates physics students taught their own group of year 9 students from Outwood City School to build and program robots to find their way around a maze. The undergraduate students spent many weeks in our labs learning to program the robots with the aim of working in groups to create a fun and educational session for the year 9 students. Each group came up with their own approach and the event was well received by all, which is a credit to our excellent first years.
You might be asking what robots has to do with physics. Well, many physics students go on to do technical roles that involve programming, such as, working in banks, physical modelling and software development. The programming of the robots has given the students an introduction to programming concepts, from loops and conditional statements to modularisation and object orientation, key building blocks for more advanced programming.
As well as learning to program, the robots receive inputs from various sensors, these include; touch/bump sensors; acoustic distance sensors; colour sensors; and gyro sensors. These sensors all rely on physical/engineering principles and this starts to develop the skills needed to understand the interaction between instruments and computer equipment which control most modern experiments.
Furthermore, this is intrinsically a team activity supporting team building and, with the teaching aspect to the year 9 students, gives the added experience of learning how to teach.
A huge thanks has to go the Venture Matrix team at Sheffield Hallam, who work alongside private, public and third party organisations from the local, national and international community to provide students with the opportunity to work on real life activities. Also, to Alex Crombie who did an amazing job in helping the first years to construct their session plans.