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.