Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 11: Magnetic Thin Films I

MA 11.8: Talk

Tuesday, March 27, 2007, 12:00–12:15, H10

Strain-controlled magnetic anisotropy of magnetite thin films — •Andreas Brandlmaier¹, Mathias Weiler¹, Stephan Geprägs¹, Matthias Opel¹, Hans Huebl², Christoph Bihler², Martin S. Brandt², Sebastian T. B. Goennenwein¹, and Rudolf Gross¹ — ¹Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany — ²Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany

Controlling the crystalline strain in ferromagnetic thin films is a promising approach to multifunctional spintronic devices, since crystalline and magnetic degrees of freedom are connected via magneto-strictive effects. We have investigated magnetite (Fe₃O₄) thin films grown on (001)-oriented MgO substrates by pulsed laser deposition. Upon attaching these samples to piezoelectric actuators such that the main actuator elongation is parallel to a magnetite [100] direction, the magnetic anisotropy of the Fe₃O₄ layer can be manipulated. We quantify the effect of the piezo-induced strain on the magnetic anisotropy by monitoring the dependence of the Fe₃O₄ ferromagnetic resonance spectrum on the voltage V applied to the actuator. We find that at room temperature, the in-plane and out-of-plane uniaxial magnetic anisotropy constants K_u^[010] and K_u^[001] can be tuned by several 10 percent and about one percent, respectively, within the range of voltages applicable to the actuator. We quantitatively compare these findings to the magneto-strictive effects expected in magnetite, using high-resolution x-ray diffraction experiments as a function of V to determine the piezo-induced crystalline strain.