Magnetic circular dichroism in x-ray absorption and core-level photoemission of Fe/Cu(001)

Conference · Wed Jul 01 04:00:00 EDT 1992

OSTI ID:7183146

Tobin, J G; Waddill, G D ^[1]; Pappas, D P ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. Naval Res., Lab., Washington, DC (United States)

We report the first observation of magnetic circular dichroism in both x-ray absorption and core-level photoemission of ultra thin magnetic films using circularly polarized x-rays. Iron films (1--4 ML) grown on a Cu(001,) substrate at 150 K and magnetized perpendicular to the surface show dramatic changes in the L[sub 2,3] branching ratio for different x-ray polarizations. For linearly-polarized x-rays perpendicular to the magnetic axis of the sample the branching ratio was 0.75. For films [ge] 2 ML, this ratio varied from 0.64 to 0.85 for photon spin parallel and anti-parallel, respectively, to the magnetic axis. This effect was observed either by changing the x-ray helcity for a fixed magnetic axis, or by reversing the magnetic axis for a fixed x-ray helicity. Our observation can be analyzed within a simple one-electron picture, if the raw branching ratios are normalized so that the linear value becomes statistical. Furthermore, warming the films to [approximately] 300 K eliminated this effect, indicating a loss of magnetization in the film over a temperature range of [approximately] 30 K. Finally, reversing the relative orientation of the photon spin and the magnetic axis from parallel to anti-parallel allowed measurement of the exchange splitting of the Fe 2p core levels which was found to be [approximately] 0.2 eV. These results are consistent with earlier studies, but the use of off-plane circularly-polarized x-rays from a bending magnet monochromator offers [approximately] 2 orders of magnitude greater intensity than typical spin-polarization measurements.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7183146
• Report Number(s): UCRL-JC-108837; CONF-920735--4; ON: DE93001305
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
BEAMS
BRANCHING RATIO
COPPER
DICHROISM
ELECTROMAGNETIC RADIATION
ELEMENTS
FILMS
IONIZING RADIATIONS
IRON
MAGNETIC CIRCULAR DICHROISM
MAGNETIZATION
METALS
POLARIZED BEAMS
RADIATIONS
SUBSTRATES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
THIN FILMS
TRANSITION ELEMENTS
X RADIATION