Tohoku University · Physics and Astronomy
Professor Mikihiko Oogane's research lab specializes in spintronics and magnetic materials, with a focus on Heusler alloys, magnetic tunnel junctions (MTJs), and ultra-sensitive magnetic field detection. The lab investigates the fundamental magnetic properties—such as Gilbert damping, spin-orbit coupling, and half-metallicity—in epitaxial Heusler alloy films, aiming to optimize their performance for spintronic devices. Key research directions include the development of high-quality Heusler-based MTJs with enhanced tunnel magnetoresistance (TMR) and the application of these materials in ultra-sensitive TMR sensors for real-time biomagnetic measurements like magnetocardiography (MCG) and nuclear magnetic resonance (NMR).
Figures are computed from collected data and may differ slightly.
We determined the Gilbert damping constants of Fe–Co–Ni and Co–Fe–B alloys with various compositions and half-metallic Co2MnAl Heusler alloy films prepared by magnetron sputtering. The ferromagnetic resonance (FMR) technique was used to determine the damping constants of the prepared films. The out-of-plane angular dependences of the resonance field (HR) and line width (ΔHpp) of FMR spectra were measured and fitted using the Landau–Lifshitz–Gilbert (LLG) equation. The experimental results fitted
We fabricated B2-ordered Co2MnAl and L21-ordered Co2MnSi Heusler alloy films by optimizing various fabrication conditions (substrate, composition of sputtering target, substrate and post-annealing temperature, etc) and applied these films to bottom electrodes of magnetic tunnel junctions (MTJs). We used Al-oxide insulating tunnel barriers for our MTJs and varied oxidation times of Al films to control qualities of the Al-oxide insulating layer and Heusler-alloy/Al-oxide interface. Observed tunnel
Abstract We developed tunnel magneto-resistive (TMR) sensors based on magnetic tunnel junctions (MTJs) that are able to detect a weak, sub-pT, magnetic field at a low frequency. Small detectivities of 0.94 pT/Hz 1/2 at 1 Hz and 0.05 pT/Hz 1/2 at 1 kHz were achieved by lowering the resistance of MTJs and enhancement of the signal using a thick CoFeSiB layer and magnetic flux concentrators. We demonstrated real-time measurement of magnetocardiography (MCG) and nuclear magnetic resonance (NMR) of p
The magnetic damping constant in a series of Co2MnAlxSi1−x and Co2FexMn1−xSi Heusler alloy epitaxial films were systematically investigated by using ferromagnetic resonance technique. The determined magnetic damping constant is roughly proportional to the density of states at the Fermi energy of the first principle calculation. The result is consistent with the theoretical prediction when taking spin-orbit interaction into account. The small Gilbert damping constant for the fabricated films othe
Co 2 Fe Si films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties (Ms and Hc), surface roughness, and magnetic damping constants (α) of the prepared Co2FeSi films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine t
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