145 research outputs found
Effect of the shape anisotropy on the magnetic configuration of (Ga,Mn)As and its evolution with temperature
We study the effect of the shape anisotropy on the magnetic domain
configurations of a ferromagnetic semiconductor (Ga,Mn)As/GaAs(001) epitaxial
wire as a function of temperature. Using magnetoresistance measurements, we
deduce the magnetic configurations and estimate the relative strength of the
shape anisotropy compared with the intrinsic anisotropies. Since the intrinsic
anisotropy is found to show a stronger temperature dependence than the shape
anisotropy, the effect of the shape anisotropy on the magnetic domain
configuration is relatively enhanced with increasing temperature. This
information about the shape anisotropy provides a practical means of designing
nanostructured spin electronic devices using (Ga,Mn)As.Comment: 4 pages, 4 figures, to appear in J. Appl. Phy
Mixed magnetic phases in (Ga,Mn)As epilayers
Two different ferromagnetic-paramagnetic transitions are detected in
(Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition
at a higher temperature results from (Ga,Mn)As cluster phases with [110]
uniaxial anisotropy and that at a lower temperature is associated with a
ferromagnetic (Ga,Mn)As matrix with cubic anisotropy. A change in the
magnetic easy axis from [100] to [110] with increasing temperature can be
explained by the reduced contribution of cubic anisotropy to the magnetic
properties above the transition temperature of the (Ga,Mn)As matrix
Epitaxial ferromagnetic FeSi/Si(111) structures with high-quality hetero-interfaces
To develop silicon-based spintronic devices, we have explored high-quality
ferromagnetic FeSi/silicon (Si) structures. Using low-temperature
molecular beam epitaxy at 130 C, we realize epitaxial growth of
ferromagnetic FeSi layers on Si (111) with keeping an abrupt interface,
and the grown FeSi layer has the ordered phase. Measurements of
magnetic and electrical properties for the FeSi/Si(111) yield a magnetic
moment of ~ 3.16 /f.u. at room temperature and a rectifying
Schottky-diode behavior with the ideality factor of ~ 1.08, respectively.Comment: 3 pages, 3 figure
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
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
Magnetic anisotropy switching in (Ga,Mn)As with increasing hole concentration
We study a possible mechanism of the switching of the magnetic easy axis as a
function of hole concentration in (Ga,Mn)As epilayers. In-plane uniaxial
magnetic anisotropy along [110] is found to exceed intrinsic cubic
magnetocrystalline anisotropy above a hole concentration of p = 1.5 * 10^21
cm^-3 at 4 K. This anisotropy switching can also be realized by post-growth
annealing, and the temperature-dependent ac susceptibility is significantly
changed with increasing annealing time. On the basis of our recent scenario
[Phys. Rev. Lett. 94, 147203 (2005); Phys. Rev. B 73, 155204 (2006).], we
deduce that the growth of highly hole-concentrated cluster regions with [110]
uniaxial anisotropy is likely the predominant cause of the enhancement in [110]
uniaxial anisotropy at the high hole concentration regime. We can clearly rule
out anisotropic lattice strain as a possible origin of the switching of the
magnetic anisotropy.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
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