Magnetic Properties of Epitaxial CoCr Films with Depth-Dependent Exchange-Coupling Profiles

Published

April 27, 2017

Author(s)

Lorenzo Fallarino, Brian Kirby, Matteo Pancaldi, Patricia Riego, Andrew L. Balk, Casey W. Miller, Paolo Vavassori, A. Berger

Abstract

We present a study of the compositional and temperature dependent magnetic properties of epitaxial CoCr thin films whose composition has a bathtub-like depth profile Co/Co_{1→1- xc}Cr_0→xc/Co_1-xcCr_xc_/Co_1-xc→1Cr_xc→0^/Co with the highest Cr concentration (xc) at the center of the sample. Polarized neutron reflectometry (PNR) shows that the effective Curie temperature varies as a function of depth and exhibits a minimum in the center of the structure. Correspondingly, we observe that the effective coupling between the two outer Co layers is strongly dependent on the magnetization of the graded CoCr spacer and can be continuously tuned via xc and temperature T. In particular, for x_c = 0.28, magnetometry reveals a transition from one-step to two-steps reversal behavior for temperatures T > 260 K, indicating a transition from a fully correlated magnetic film structure to an uncoupled system containing effectively two independent magnetic sublayers. Corroborating evidence of the temperature dependent coupling of the top and bottom regions for x_c = 0.28 was revealed by PNR, which demonstrated the field dependent occurrence of antiparallel magnetization alignment on opposite interfaces at sufficiently high temperatures only.

Citation

Physical Review B

Volume

95

Issue

13

Pub Type

Journals

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Citation

Fallarino, L. , Kirby, B. , Pancaldi, M. , Riego, P. , Balk, A. , Miller, C. , Vavassori, P. and Berger, A. (2017), Magnetic Properties of Epitaxial CoCr Films with Depth-Dependent Exchange-Coupling Profiles, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922283 (Accessed January 20, 2025)