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Structural and Magnetic X-RAY Scattering Measurements of Epitaxial Dy thin Films

Published online by Cambridge University Press:  26 February 2011

Michael F. Toney
Affiliation:
IBM Research Division, Almaden Research Center, 650 Harry Road, San.Tose, California 95120-6099.
David G. Wiesler
Affiliation:
IBM Research Division, Almaden Research Center, 650 Harry Road, San.Tose, California 95120-6099.
Brent D. Hermsmeier
Affiliation:
IBM Research Division, Almaden Research Center, 650 Harry Road, San.Tose, California 95120-6099.
Robin F. Farrow
Affiliation:
IBM Research Division, Almaden Research Center, 650 Harry Road, San.Tose, California 95120-6099.
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Abstract

We report structural and magnetic X-ray scattering measurements of a 2000Å thick Dy film, sandwiched by LaF3 films on a GaAs(111) substrate. The structure was grow by molecular beam epitaxy with the c-axis of the Dy parallel to the LaF3 c-axis and GaAs[111] axis. For the magnetic X-ray scattering, we used a polarization analyzer and an X-ray energy near the Dy L111 absorption edge. ∆t this energy there is a resonant enhancement in the magnetic scattering intensity, and we obtained ≃-50 counts per second in the magnetic diffraction peaks.

Between 85 and 179K, bulk Dy forms a helical antiferromagnetic structure, and below 85K, it transforms into a ferromagnet. We find that the c-axis lattice constant of the Dy film has a similar temperature dependence to bulk Dy from room temperature to about 110K, but below this, the film behaves differently from bulk and is strained. The temperature dependence of the turn-angle in the helical antiferromagnetic state is similar to bulk, although a weaker dependence is observed below ∼1 10K due to magnetoelastic effects. Surprisingly, the magnetic coherence length (≃310Å) is significantly shorter than the structural coherence length (≃730Å). The transition to ferromagnetic ordering at 86K exhibits temperature hysteresis as is evident in the structural and magnetic X-ray data and in SQUID magnetometry data. We believe this hysteresis arises from a combination of the strain-energy barrier accompanying the transition and magnetic inhomogeneities in the film.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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