Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets

Published

February 6, 2018

Author(s)

Lorenzo Fallarino, P. Riego, Brian Kirby, Casey W. Miller

Abstract

Ferromagnetic alloy materials with designed dopant 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 given that they exhibit easy to tune magnetic properties such as saturation magnetization M_s and Curie temperature T_c while preserving their crystalline structure in a wide composition range. In order to demonstrate this materials design potential, we have grown a series of graded Co_1-xCr_x and Co_1-wRu_w (1010) epitaxial thin films, with x and we following predefined doping 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 an in-plane easy magnetic axis to suppress magnetostatic domain generation. Temperature and field-dependent magnetic depth profiles have been measured by means of polarized neutron reflectometry. In both investigated structures, T_c and M_s are found to vary as a function of depth in accordance with the predefined compositional depth profiles. Our Co_1-wRu_w sample structures, which exhibit very steep material gradients, allow the determination of the localization limit for compositionally graded material, which we find to be of the order of 1 nm. The Co_1-xCr_x systems show the expected U-shaped T_c and M_s 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 samples parts at elevated temperatures.

Citation

Materials

Volume

11

Issue

2

Pub Type

Journals

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Keywords

magnetism

Citation

Fallarino, L. , Riego, P. , Kirby, B. and Miller, C. (2018), Modulation of Magnetic Properties at the Nanometer Scale in Continuously Graded Ferromagnets, Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925052 (Accessed April 23, 2024)