NSLS-II Colloquium Series

What is the smallest possible size of a magnet? How fast can we switch the magnetization of a thin film? The answer to these simple questions reveals a fascinating world of interactions, which are largely dominated by interface effects. Understanding and controlling such interactions opens new perspectives for classical and quantum data processing technologies at the microscopic scale. Synchrotron radiation measurements exploiting x-ray dichroism at the L- and M-edges of the transition metal and lanthanide elements, respectively, provide a unique spectroscopic and microscopic tool to link the nanoscale properties of matter to the magnetic behavior of different classes of materials. In this talk, I will describe our studies of the evolution of magnetism from single atoms to nanoparticles and molecular magnets [1-4], focusing on the conditions required to achieve magnetic bistability in small systems [5,6]. I will further report on recent efforts to induce magnetization switching using electrical currents in materials characterized by strong spin-orbit interactions [7,8]. Current pump/x-ray probe experiments reveal the mechanism and time scale of magnetization reversal induced by the spin–orbit torques and spin Hall effect in thin film heterostructures, which has applications in ultrafast magnetic random access memories with high endurance [9,10].

[1] P. Gambardella et al., Phys. Rev. Lett. 88, 047202 (2002).
[2] P. Gambardella et al., Science 300, 1130 (2003).
[3] P. Gambardella et al., Nature Mater. 8, 189 (2009).
[4] S. Stepanow et al., J. Am. Chem. Soc. 136, 5451 (2014).
[5] I. G. Rau et al., Science 344, 988 (2014).
[6] F. Donati et al., Science 352, 318 (2016).
[7] I. M. Miron et al., Nature 476, 189 (2011).
[8] K. Garello et al., Nature Nanotech. 8, 587 (2013).
[9] M. Baumgartner et al., Nature Nanotech., in press (2017).
[10] G. Prenat et al., IEEE Transactions on Multi-Scale Computing 2, 149 (2016).