Spin structure at nanojunctions and constrictions

Abstract

A micromagnetic Green-function approach is used to investigate the effect of nanojunctions, constraints, and other obstacles on spin-dependent conduction. Depending on geometry, the determination of the spin structure involves several types of Bessel functions. A common feature of the Green functions is the involvement of the domain-wall width of the main phase, which can be interpreted as the decay length of the magnetization perturbation away from the junction. This length is typically on the order of 10 nm and independent of the strength of the perturbation. Only the magnitude of the magnetization perturbation depends on the strength of the inhomogenity. A particular feature of the considered structures is that the total spin-dependent scattering cross section, as estimated from the squared magnetization gradient, exhibits a characteristic real-structure dependent maximum as a function of the boundary phase or junction dimensions.

Magnetic properties of core/shell nanoparticles with magnetic or nonmagnetic shells

“…In equation ( 4), we can neglect the term ∇A∇m. The physical meaning of this term is that the term ∇A(r) in equation ( 4) reflects the local character of the exchange stiffness A(r) which can be neglected in calculations [26,27]. Except for the ∇A∇m term, equation ( 4) is equivalent to Schrödinger's equation for an electron in electrostatic potential V .…”

Micromagnetic calculation of the magnetization process in nanocontacts

“…The equilibrium magnetization state is calculated Tatara et al reported domain wall scattering in the nanoconstriction. Since the penetration length ␦ in the soft material is known to be ␦ = ͱ A /4M s 2 , which is proportional to the domain wall width D, 8 varying the values of W and L is equivalent to varying the effective exchange stiffness constant. The domain wall scattering is very sensitive to the domain wall width, which is very important in order to understand anomalous large magnetoresistance in the nanoconstriction.…”

“…1-6 A very large magnetoconductance effect in the ferromagnetic nanoconstriction of T-shaped Ni wire has been reported by Garcia et al 2 Tatara et al suggested that the magnetic domain wall pinned in nanoconstriction explains the large magnetoconductance effect. 8,9 Skomski and Sellmyer 8 suggested that the exchange stiffness is very important for pinning the domain wall at nanojunctions. In addition, the local magnetization distribution at nanojunctions/nanoconstrictions have been reported in various studies.…”