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



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


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/Co1→1- xcCr0→xc/Co1-xcCrxc/Co1-xc→1Crxc→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 xc = 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 xc = 0.28 was revealed by PNR, which demonstrated the field dependent occurrence of antiparallel magnetization alignment on opposite interfaces at sufficiently high temperatures only.
Physical Review B


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], (Accessed February 23, 2024)
Created April 26, 2017, Updated October 12, 2021