3 research outputs found
Magnetic anisotropy of epitaxial (Ga,Mn)As on (113)A GaAs
The temperature dependence of magnetic anisotropy in (113)A (Ga,Mn)As layers
grown by molecular beam epitaxy is studied by means of superconducting quantum
interference device (SQUID) magnetometry as well as by ferromagnetic resonance
(FMR) and magnetooptical effects. Experimental results are described
considering cubic and two kinds of uniaxial magnetic anisotropy. The magnitude
of cubic and uniaxial anisotropy constants is found to be proportional to the
fourth and second power of saturation magnetization, respectively. Similarly to
the case of (001) samples, the spin reorientation transition from uniaxial
anisotropy with the easy along the [-1, 1, 0] direction at high temperatures to
the biaxial anisotropy at low temperatures is observed around 25 K. The
determined values of the anisotropy constants have been confirmed by FMR
studies. As evidenced by investigations of the polar magnetooptical Kerr
effect, the particular combination of magnetic anisotropies allows the
out-of-plane component of magnetization to be reversed by an in-plane magnetic
field. Theoretical calculations within the p-d Zener model explain the
magnitude of the out-of-plane uniaxial anisotropy constant caused by epitaxial
strain, but do not explain satisfactorily the cubic anisotropy constant. At the
same time the findings point to the presence of an additional uniaxial
anisotropy of unknown origin. Similarly to the case of (001) films, this
additional anisotropy can be explained by assuming the existence of a shear
strain. However, in contrast to the (001) samples, this additional strain has
an out-of-the-(001)-plane character.Comment: 13 pages, 9 figure
Structural and paramagnetic properties of dilute Ga1-xMnxN
Systematic investigations of the structural and magnetic properties of single
crystal (Ga,Mn)N films grown by metal organic vapor phase epitaxy are
presented. High resolution transmission electron microscopy, synchrotron x-ray
diffraction, and extended x-ray absorption fine structure studies do not reveal
any crystallographic phase separation and indicate that Mn occupies
Ga-substitutional sites in the Mn concentration range up to 1%. The magnetic
properties as a function of temperature, magnetic field and its orientation
with respect to the c-axis of the wurtzite structure can be quantitatively
described by the paramagnetic theory of an ensemble of non-interacting
Mn ions in the relevant crystal field, a conclusion consistent with the
x-ray absorption near edge structure analysis. A negligible contribution of Mn
in the 2+ charge state points to a low concentration of residual donors in the
studied films. Studies on modulation doped p-type (Ga,Mn)N/(Ga,Al)N:Mg
heterostructures do not reproduce the high temperature robust ferromagnetism
reported recently for this system.Comment: 15 pages, 14 figure