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Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Thin Films: Magnetic Coupling Phenomena / Exchange Bias

MA 26.3: Vortrag

Dienstag, 21. März 2017, 14:30–14:45, HSZ 101

Depth dependent magnetic structure of graded Co-alloy thin films — •Lorenzo Fallarino1, Brian J. Kirby2, Matteo Pancaldi1, Patricia Riego1, Casey W. Miller3, Paolo Vavassori1,4, and Andreas Berger11CIC nanoGUNE, Spain — 2NCNR-NIST, USA — 3RIT, USA — 4IKERBASQUE, Spain

We present a study aimed at the precise tailoring of exchange coupling strength along the surface normal of sputter deposited Cobalt-Chromium (Co1−xCrx) and Cobalt-Ruthenium (Co1−xRux) alloy thin films. We have grown a series of such compositionally graded epitaxial thin films, in which the Co content (1-x) has an overall bathtub-shaped profile along the surface normal. In addition to conventional magnetometry, temperature and field-dependent magnetic depth profiles have been measured by using polarized neutron reflectometry (PNR). The effective Curie temperature is found to vary as a function of depth, exhibiting a minimum in the center of the structure, which verifies the structurally and magnetically graded modulation. PNR also verified that the effective coupling in between the Co-rich outer layers is dependent on the magnetization of the central layer, and thus the overall magnetic reversal can be tuned continuously via temperature from a square hysteresis loop to a two-steps behavior. In addition, we have explored oscillatory Curie temperature structures of different wavelengths λ produced by a triangular Ru content profile, oscillating in between x = 0.22 and x = 0.28. By changing λ, we have investigated the possible length scales, in which compositional effects can be transferred into modulated magnetic states for such itinerant ferromagnets.

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