Optimizing magneto-optical effects in the ferromagnetic semiconductor GaMnAs

Abstract

A trilayer of the ferromagnetic semiconductor GaMnAs, a SiO 2 buffer layer and a piezoelectric ZnO layer is investigated in view of its use in device implementation to study surface acoustic wave assisted magnetization switching. The magneto-optical properties: Kerr rotation and ellipticity and magnetic contrast in Kerr microscopy images are investigated as a function of temperature. While the ZnO layer prevents any good quality imaging of magnetic domains, we show that with the SiO 2 layer only the polar Kerr rotation and the magnetic contrast are increased by a factor 2. This result is in good quantitative agreement with calculations using an optical interference model and could be further improved. The detrimental effects of the dielectric layers overgrowth on the Curie temperature and coercive field of the GaMnAs layer can be kept to a reasonable level.

Precessional magnetization switching by a surface acoustic wave

“…This wide dispersion was probably caused by the deposition of the piezoelectric layer. We had already shown it to deteriorate the Curie temperature [19,38].…”

“…The piezoelectric layer consists of 250 nm of ZnO, deposited over 70 nm of SiO 2 , necessary for good adhesion. The thickness of the SiO 2 layer was designed to increase the Kerr contrast [38]. The interdigitated transducers (IDTs) are made out of Cr/Au (thickness 10/80 nm) with a metallization ratio of 0.5 and teeth width 1.25 μm.…”

Magneto-optical Kerr spectroscopy of (Ga,Mn)(As,P) ferromagnetic layers: Experiments and k.p theory

“…These values are consistent with previous reports in (Ga,Mn)As compounds. 25,26,29,30,32,57 Let us note however that their respective amplitudes depend on the layer thickness (Eq. (3)).…”

Strong reduction of the coercivity by a surface acoustic wave in an out-of-plane magnetized epilayer

“…The IDT teeth were 1.25 μm wide and equidistant, giving a SAW wavelength of 5 μm and frequency of f SAW = 549 MHz (SAW period T SAW ≈ 1.8 ns). A window etched in the ZnO layer between the two IDTs facilitated the Kerr imaging, with the SiO 2 layer thickness adjusted for an optimal Kerr contrast [22] at λ = 600 nm. Whereas the IDTs are separated by 2 mm, the typical field of view for the polar Kerr microscope is between 360 and 994 μm wide, depending on the magnification used [ Fig.…”