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Unidirectional motion of magnetic domain walls is the key concept underlying next-generation domain-wall-mediated memory and logic devices. Such motion has been achieved either by injecting large electric currents into nanowires or by employing domain-wall tension induced by sophisticated structural modulation. Herein, we demonstrate a new scheme without any current injection or structural modulation. This scheme utilizes the recently discovered chiral domain walls, which exhibit asymmetry in their speed with respect to magnetic fields. Because of this asymmetry, an alternating magnetic field results in the coherent motion of the domain walls in one direction. Such coherent unidirectional motion is achieved even for an array of magnetic bubble domains, enabling the design of a new device prototype—magnetic bubblecade memory—with two-dimensional data-storage capability.

We have probed one antiferromagnetic (AF) antiphase boundary (APB) and a single Fe(3)O(4) domain using nanogap contacts. Our experiments directly demonstrate that, in the case of probing one AF-APB, a large magnetoresistance (MR), high resistivity, and a high saturation field are observed as compared with the case of probing a single Fe(3)O(4) domain. The shape of the temperature-dependent MR curves is also found to differ between the single domain and one of the AF-APB measurements, with a characteristic strong temperature dependence for the single domain and temperature independence for the one AF-APB case. We argue that these observations are indicative of profound changes in the electronic transport across APBs. The investigated APB defects increase the activation energy and disturb the long-range charge ordering of monodomain Fe(3)O(4).

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