Regensburg 2022 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 22: Thin Films: Magnetic Coupling Phenomena / Exchange Bias / Magnetic Anisotropy
MA 22.5: Vortrag
Mittwoch, 7. September 2022, 10:30–10:45, H47
Temperature independent coercivity by means of nanoscale materials design — •Mikel Quintana1, Adrián Meléndez1,2, Carmen Martín Valderrama1, Lorenzo Fallarino1, and Andreas Berger1 — 1CIC nanoGUNE BRTA, E-20018 Donostia-San Sebastián, Spain — 2UPV/EHU, E-48940 Bizkaia, Spain
Thin film materials, in which the exchange coupling strength is designed to be depth-dependent, behave at each depth as if their properties were controlled by a “local” Curie temperature Tcloc, down to the 1-2 nm length-scale [1]. This phenomenon enables the control and design of ferromagnetic (FM) magnetization profiles as a function of temperature T. For instance, it allows one to engineer films exhibiting FM exchange-coupling everywhere, but which can split into separate multilayers exhibiting seemingly isolated FM states in certain T-ranges. Here, we present a multilayer system composed by two CoRu films separated by a graded Co1−x(z)Rux(z) spacer layer with varying Ru concentration x along the depth z of the film. The spacer layer is such that an effective-PM-state thickness dividing two FM films decreases when reducing T. This specific materials design allows us to obtain a coercive field Hc plateau in an extended temperature range, in which Hc changes less than 2% between 150 K and 225 K, while conventional films exhibit a change of 20% in the same T-range. The stable coercivity plateau can be designed at any temperature by means of an adapted Tcloc(z) design, enabling T-independent operation points for technological applications. [1] L. Fallarino et. al., Materials 11, 251 (2018).