Magnetization Reversals Of Fe81ga19-Based Flexible Thin Films Under Multiaxial Mechanical Stress

The effect of multiaxial mechanical stress on angle-dependent magnetization reversals is studied on a single 10-nm Ni80Fe20 film, a single 10-nm Fe81Ga19 film, and a Ni80Fe20(10 nm)/Fe81Ga19(10 nm) bilayer. These films are grown on flexible Al ?kitchenlike? foils. These flexible foils are bent on two convex optical lenses to apply multiaxial mechanical stresses of different magnitudes. In order to understand the mechanisms driving the physical properties of the flexible systems, the magnetic films are also grown on hard native-oxide-covered Si(100) substrates. By probing the angular dependence of the coercive field and the remanent magnetization, we show that the Ni80Fe20 single layer and the Ni80Fe20/Fe81Ga19 bilayer grown on Si present a uniaxial anisotropy. Along their easy axis, their domain structure at the coercive field exhibits large domains with sawtooth domain walls. However, the Fe81Ga19 layer grown on Si shows a cubic anisotropy and sharp domain walls with a right-angle geometry along its easy axis. All layers grown on Al foils show development or enhancement of a uniaxial anisotropy arising from the Al surface morphology. Multiaxial mechanical stress applied to the flexible Al foils results in very different nonreversible effects as a function of the composition of the layered system. For Ni80Fe20, multiaxial mechanical stress has no effect, as expected for a nonmagnetostrictive system. For Fe81Ga19, it results in a full in-plane randomization of its magnetization-reversal properties. For the bilayer, multiaxial mechanical stress does not fully randomize the in-plane magnetization-reversal properties: the bilayer retains a uniaxial character.