Spin-polarized electron energy loss spectroscopy

Spin-polarized electron energy loss spectroscopy or SPEELS is a technique mainly used to measure the dispersion relation of the collective excitations, over the whole Brillouin zone.

Spin waves are collective perturbations in a magnetic solid. Their properties depend on their wavelength (or wave vector). For long wavelength (short wave vector) spin waves, the resulting spin precession has a very low frequency and the spin waves can be treated classically. Ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) experiments explain the long wavelength spin waves in ultrathin magnetic films and nanostructures. If the wavelength is comparable to the lattice constant, the spin waves are governed by the microscopic exchange coupling and a quantum mechanical description is needed. Therefore, experimental information on these short wavelength (large wave vector) spin waves in ultrathin films is highly desired and may lead to fundamentally new insights into the spin dynamics in reduced dimensions in the future.

SPEELS is one of the few techniques that can be used to measure the dispersion of such short wavelength spin waves in ultrathin films and nanostructures.{{Citation needed|date=April 2021}}

The first experiment

For the first time Kirschner's group{{cite web|url=http://www.mpi-halle.de/~wme1/ |title=MPI MSP-Exp. Dept. I: Welcome |publisher=Mpi-halle.de |date= |accessdate=2009-12-18}} in Max Planck institute of Microstructure Physics showed that the signature of the large wave vector spin waves can be detected by spin polarized electron energy loss spectroscopy (SPEELS).{{cite journal | last1=Plihal | first1=M. | last2=Mills | first2=D. L. | last3=Kirschner | first3=J. | title=Spin Wave Signature in the Spin Polarized Electron Energy Loss Spectrum of Ultrathin Fe Films: Theory and Experiment | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=82 | issue=12 | date=22 March 1999 | issn=0031-9007 | doi=10.1103/physrevlett.82.2579 | pages=2579–2582}}{{cite journal | last1=Ibach | first1=H. | last2=Bruchmann | first2=D. | last3=Vollmer | first3=R. | last4=Etzkorn | first4=M. | last5=Anil Kumar | first5=P. S. | last6=Kirschner | first6=J. | title=A novel spectrometer for spin-polarized electron energy-loss spectroscopy | journal=Review of Scientific Instruments | publisher=AIP Publishing | volume=74 | issue=9 | year=2003 | issn=0034-6748 | doi=10.1063/1.1597954 | pages=4089–4095| url=http://juser.fz-juelich.de/record/32120 }} Later, with a better momentum resolution, the spin wave dispersion was fully measured in 8 monolayer (ML) fcc cobalt film on Cu(001){{cite journal | last1=Vollmer | first1=R. | last2=Etzkorn | first2=M. | last3=Kumar | first3=P. S. Anil | last4=Ibach | first4=H. | last5=Kirschner | first5=J. | title=Spin-Polarized Electron Energy Loss Spectroscopy of High Energy, Large Wave Vector Spin Waves in Ultrathin fcc Co Films on Cu(001) | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=91 | issue=14 | date=29 September 2003 | issn=0031-9007 | doi=10.1103/physrevlett.91.147201 | pmid=14611549 | page=147201| url=http://juser.fz-juelich.de/record/31315/files/31644.pdf }} and 8 ML hcp cobalt on W(110),{{cite journal | last1=Etzkorn | first1=M. | last2=Anil Kumar | first2=P. S. | last3=Tang | first3=W. | last4=Zhang | first4=Y. | last5=Kirschner | first5=J. | title=High-wave-vector spin waves in ultrathin Co films on W(110) | journal=Physical Review B | publisher=American Physical Society (APS) | volume=72 | issue=18 | date=16 November 2005 | issn=1098-0121 | doi=10.1103/physrevb.72.184420 | page=184420}} respectively. Those spin waves were obtained up to the surface Brillouin zone (SBZ) at the energy range about few hundreds of meV. Another recent example is the investigation of 1 and 2 monolayer iron films grown on W(110) measured at 120 K and 300 K, respectively.{{cite journal | last1=Tang | first1=W. X. | last2=Zhang | first2=Y. | last3=Tudosa | first3=I. | last4=Prokop | first4=J. | last5=Etzkorn | first5=M. | last6=Kirschner | first6=J. | title=Large Wave Vector Spin Waves and Dispersion in Two Monolayer Fe onW(110) | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=99 | issue=8 | date=24 August 2007 | issn=0031-9007 | doi=10.1103/physrevlett.99.087202 | pmid=17930976 | page=087202}}{{cite journal | last1=Prokop | first1=J. | last2=Tang | first2=W. X. | last3=Zhang | first3=Y. | last4=Tudosa | first4=I. | last5=Peixoto | first5=T. R. F. | last6=Zakeri | first6=Kh. | last7=Kirschner | first7=J. | title=Magnons in a Ferromagnetic Monolayer | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=102 | issue=17 | date=30 April 2009 | issn=0031-9007 | doi=10.1103/physrevlett.102.177206 | page=177206| pmid=19518825 }}

References

Category:Scattering

Category:Electron spectroscopy

Category:Scientific techniques