Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets
CIC nanoGUNE, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian, Spain
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
Departamento de Física de la Materia Condensada, Universidad del País Vasco, UPV/EHU, E-48080 Bilbao, Spain
NIST Center for Neutron Research, NIST, Gaithersburg, MD 20899, USA
School of Chemistry and Materials Science, Rochester Institute of Technology, Rochester, NY 14623, USA
Author to whom correspondence should be addressed.
Received: 19 December 2017 / Revised: 25 January 2018 / Accepted: 31 January 2018 / Published: 6 February 2018
Ferromagnetic alloy materials with designed composition depth profiles provide an efficient route for the control of magnetism at the nanometer length scale. In this regard, cobalt-chromium and cobalt-ruthenium alloys constitute powerful model systems. They exhibit easy-to-tune magnetic properties such as saturation magnetization MS
and Curie temperature TC
while preserving their crystalline structure over a wide composition range. In order to demonstrate this materials design potential, we have grown a series of graded Co1−x
0) epitaxial thin films, with x
following predefined concentration profiles. Structural analysis measurements verify the epitaxial nature and crystallographic quality of our entire sample sets, which were designed to exhibit in-plane c
-axis orientation and thus a magnetic in-plane easy axis to achieve suppression of magnetostatic domain generation. Temperature and field-dependent magnetic depth profiles have been measured by means of polarized neutron reflectometry. In both investigated structures, TC
are found to vary as a function of depth in accordance with the predefined compositional depth profiles. Our Co1−w
sample structures, which exhibit very steep material gradients, allow us to determine the localization limit for compositionally graded materials, which we find to be of the order of 1 nm. The Co1−x
systems show the expected U-shaped TC
depth profiles, for which these specific samples were designed. The corresponding temperature dependent magnetization profile is then utilized to control the coupling along the film depth, which even allows for a sharp onset of decoupling of top and bottom sample parts at elevated temperatures.
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MDPI and ACS Style
Fallarino, L.; Riego, P.; Kirby, B.J.; Miller, C.W.; Berger, A. Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets. Materials 2018, 11, 251.
Fallarino L, Riego P, Kirby BJ, Miller CW, Berger A. Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets. Materials. 2018; 11(2):251.
Fallarino, Lorenzo; Riego, Patricia; Kirby, Brian J.; Miller, Casey W.; Berger, Andreas. 2018. "Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets." Materials 11, no. 2: 251.
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