Domain-wall magnetoresistance of Co nanowires

Abstract

Using density functional theory implemented within a tight-binding linear muffin-tin orbital method we perform calculations of electronic, magnetic, and transport properties of ferromagnetic free-standing fcc Co wires with diameters up to 1.5 nm. We show that finite-size effects play an important role in these nanowires resulting in oscillatory behavior of electronic charge and the magnetization as a function of the wire thickness, and a nonmonotonic behavior of spin-dependent quantized conductance. We calculate the magnetoresistance ͑MR͒ of a domain wall ͑DW͒ modeled by a spin-spiral region of finite width sandwiched between two semi-infinite Co wire leads. We find that the DW MR decreases very rapidly, on the scale of a few interatomic layers, with the increasing DW width. The largest MR value of about 250% is predicted for an abrupt DW in the monatomic wire. We show that, for some energy values, the density of states and the conductance may be nonzero only in one spin channel, making the MR for the abrupt DW infinitely large. We also demonstrate that for the abrupt DW a large MR may occur due to the hybridization between two spin subbands across the DW interface. We do not find, however, such a behavior at the Fermi energy for the Co wires considered.

Quantized magnetoresistance in atomic-size contacts

“…During these events, the conductance plateaux at multiples of e 2 /h provide a clear signature of the occurrence of ballistic transport. Conductance plateaux lasting up to hundreds of seconds are realized by adequate tuning of deposition (dissolution) at electrochemical reduction (oxidation) potentials of Co. Interestingly, many Co samples show rather stable conductance at 5, 6 and 7e 2 /h, consistent with the theoretical predictions for ballistic transport in atomic-size Co wires 27 . Angular-dependence experiments were performed on a contact that did not change during the rotation period.…”

Positive antiphase boundary domain wall magnetoresistance in Fe3O4(110) heteroepitaxial films

“…[1][2][3][4][5] Research activity in this area has increased substantially in the recent past due to the advances in material preparation and various nanofabrication techniques which allow one to control the DW dimensions and their number. [6][7][8][9] The origin of the DW resistance (DWR) in ferromagnetic metals is attributed to the mixing of up-and down-spin electrons due to the spin mistracking of the electrons on passing through the DW. 3 However, the models proposed for the ferromagnetic metals cannot be applied generally; for example, it is not sufficient to explain the DWR observed in itinerant ferromagnets such as SrRuO 3 .…”

“…11,12,[22][23][24][25][26][27] MgO (lattice constant 0.4212 nm), which has a rock salt crystal structure, is a widely used substrate for epitaxy of magnetite (lattice constant 0.83987 nm) due to the small lattice mismatch of only 0.33%. 9 Antiphase boundaries (APB) are structural defects occurring in thin films during epitaxial growth and are observed in Fe 3 O 4 films when grown on a variety of substrates like MgO, MgAl 2 O 4 , and α-Al 2 O 3 . 11,12,[28][29][30] Since the Fe 3 O 4 (Fd3m) crystal structure is of lower symmetry than MgO (Fm3m), there are several equivalent nucleation sites on the MgO (100) surface, which enforce the formation of APBs at the interface of the neighboring grains.…”

Magnetic Moment Softening and Domain Wall Resistance in Ni Nanowires

“…The theoretical description of the DW resistance so far was based on either free-electron models [13] in which the DW is represented by an appropriate potential profile or first-principles calculations [14,15] in which the DW is typically described by a spin-spiral structure. All these models assume that the DW is rigid; i.e., they neglect any spatial variation of the magnitude of the magnetic moment across the DW.…”