Out-of-plane, nanoscale periodic corrugations are observed in the dynamic fracture surface of brittle bulk metallic glasses with fracture toughness approaching that of silica glasses. A model based on the meniscus instability and plastic zone theory is used to explain such dynamic crack instability. The results indicate that the local softening mechanism in the fracture is an essential ingredient for controlling the formation of the unique corrugations, and might provide a new insight into the origin of fracture surface roughening in brittle materials.

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A two-turn, eight-armed, rectangular Si/Ni heterogeneous nanospring structure on Si(100) has been fabricated using a multilayer glancing-angle deposition technique. The multilayered nanosprings with a height of approximately 1.98 mum were composed of alternating layers of amorphous Si nanorods approximately 580 nm in length and face-centered cubic Ni nanorods approximately 420 nm in length, both with a diameter of approximately 35 nm. The magnetic anisotropy of the nanosprings showed that the in-plane easy and hard axes were parallel and perpendicular to the Ni nanorod plane, respectively. The out-of-plane magnetic hysteresis loop was very sensitive to the applied magnetic field direction when rotating the nanosprings about their in-plane hard axis, and the magnetization measurement revealed that the nanosprings tilted at approximately 7.5 degrees toward the plane of the Si nanorods. The magnetic anisotropy of the nanosprings is determined by their structure, and the experimental results can be interpreted by the shape anisotropy energy.

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