Giant magnetoresistance due to a domain wall in Fe: Ab initio study

The magnetoresistance due to a domain wall in pure Fe was studied theoretically by means of ab initio electronic structure calculations based on a linear muffin-tin orbital method modified for noncollinear magnets. The Bloch walls were modeled by a superlattice structure in the (001) direction of the bcc lattice with alternating regions of collinear and spiral-like magnetizations. The conductivity was calculated by means of the linearized Boltzmann equation in a relaxation time approximation. The magnetoresistance due to a domain wall (DW) is presented as a function of the angle between the magnetizations, domain-wall thickness, and domain size. The orientation dependence of the magnetoresistance due to a DW in pure Fe has cos-like behavior in contrary to the giant magnetoresistance in Fe/Cr superlattices. It was also shown that the presence of Cr increases the GMR amplitude in comparison with pure Fe separated by a noncollinear domain wall of equal size. The Kronig-Penney model was used in order to show that the oscillations of GMR as a function of domain size stem from quantum well states crossing the Fermi level.