Resistance of single magnetic domain walls and its size effect in half-metallic CrO₂ epitaxial nanostructures

Magnetic domain walls can be used to induce large magnetoresistance (MR) and hence are viewed as active electron transport agents, particularly in half-metallic solids with 100% spin polarization. In this talk, we will report a study of the size effect on excess resistance induced by a single magnetic domain wall in a one-dimensional half-metallic CrO₂ nanoscale conductor. We grow an asymmetric built-in constriction whose channel width (d) ranges from 30 to 200 nm and measure their MR. We observe repeatable and reversible MR jumps by sweeping a magnetic field. The MR jumps are interpreted as the domain-wall resistance (DMR) induced by the creation and annihilation of a single magnetic domain wall near the constricted neck. We confirm the field dependence of the magnetic configuration through micromagnetic simulation studies. Our results suggest a large size effect of d on the DMR, as the DMR scales with d as d^-1.87±0.32. Accordingly, we predict that the MR ratio of a simple CrO₂ nanowire impregnated with a constriction at a 150 nm² cross section could reach 100%. This large MR far exceeds that of a conventional ferromagnetic nanowire, confirming the role of half metallicity on enhanced magneto transport. The large DMR can be taken advantage of in the construction of spintronic devices such as magnetic sensing or memory.