543 research outputs found
Ion Irradiation Control of Ferromagnetism in (Ga,Mn)As
We report on a promising approach to the artificial modification of
ferromagnetic properties in (Ga,Mn)As using a Ga focused ion beam (FIB)
technique. The ferromagnetic properties of (Ga,Mn)As such as magnetic
anisotropy and Curie temperature can be controlled using Ga ion
irradiation, originating from a change in hole concentration and the
corresponding systematic variation in exchange interaction between Mn spins.
This change in hole concentration is also verified using micro-Raman
spectroscopy. We envisage that this approach offers a means of modifying the
ferromagnetic properties of magnetic semiconductors on the micro- or nano-meter
scale.Comment: 4 pages, 4 figures, to appear in Jpn. J. Appl. Phys. (Part 2 Letters
Effect of Ga irradiation on magnetic and magnetotransport properties in (Ga,Mn)As epilayers
We report on the magnetic and magnetotransport properties of ferromagnetic
semiconductor (Ga,Mn)As modified by Ga ion irradiation using focused ion
beam. A marked reduction in the conductivity and the Curie temperature is
induced after the irradiation. Furthermore, an enhanced negative
magnetoresistance (MR) and a change in the magnetization reversal process are
also demonstrated at 4 K. Raman scattering spectra indicate a decrease in the
concentration of hole carriers after the irradiation, and a possible origin of
the change in the magnetic properties is discussed
Alternating domains with uniaxial and biaxial magnetic anisotropy in epitaxial Fe films on BaTiO[sub 3]
We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastica–c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelasticanisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a–c domain pattern in the Fe films. Exchange and magnetostaticinteractions between neighboring magnetic stripes further influence magnetization reversal and pattern formation within the a and c domains.Peer reviewe
Spin dependent scattering of a domain-wall of controlled size
Magnetoresistance measurements in the CPP geometry have been performed on
single electrodeposited Co nanowires exchange biased on one side by a sputtered
amorphous GdCo layer. This geometry allows the stabilization of a single domain
wall in the Co wire, the thickness of which can be controlled by an external
magnetic field. Comparing magnetization, resistivity, and magnetoresistance
studies of single Co nanowires, of GdCo layers, and of the coupled system,
gives evidence for an additional contribution to the magnetoresistance when the
domain wall is compressed by a magnetic field. This contribution is interpreted
as the spin dependent scattering within the domain wall when the wall thickness
becomes smaller than the spin diffusion length.Comment: 9 pages, 13 figure
Spintronic transport and Kondo effect in quantum dots
We investigate the spin-dependent transport properties of quantum-dot based
structures where Kondo correlations dominate the electronic dynamics. The
coupling to ferromagnetic leads with parallel magnetizations is known to give
rise to nontrivial effects in the local density of states of a single quantum
dot. We show that this influence strongly depends on whether charge
fluctuations are present or absent in the dot. This result is confirmed with
numerical renormalization group calculations and perturbation theory in the
on-site interaction. In the Fermi-liquid fixed point, we determine the
correlations of the electric current at zero temperature (shot noise) and
demonstrate that the Fano factor is suppressed below the Poissonian limit for
the symmetric point of the Anderson Hamiltonian even for nonzero lead
magnetizations. We discuss possible avenues of future research in this field:
coupling to the low energy excitations of the ferromagnets (magnons), extension
to double quantum dot systems with interdot antiferromagnetic interaction and
effect of spin-polarized currents on higher symmetry Kondo states such as
SU(4).Comment: 11 pages, 5 figures. Proceedings of the 3rd Intl. Conf. on Physics
and Applications of Spin-Related Phenomena in Semiconductors, Santa Barbara,
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