GaMnAs Research Articles

Magneto-Optical Detection of the Intrinsic Ferromagnetism and Phase Separation in Diluted Magnetic Semiconductors

Abstract—Spectral and temperature dependences of the magneto-optical transversal Kerr effect (TKE) of GaMnAs layers prepared by different methods are reported in this work. The GaMnAs layers prepared by pulsed laser sputtering at 300°С demonstrate a ferromagnetic behavior below 80 K, which is due to the presence of local ferromagnetic (Ga,Mn)As areas in the paramagnetic matrix. The Ga(In)MnAs layers prepared by ion implantation and subsequent pulsed laser annealing were found to exhibit a high TKE response at low temperatures. The presence of the characteristic band in the TKE spectrum in the range of transitions near the L point of the band structure of Ga(In)As confirms the intrinsic ferromagnetism. The temperature dependences of TKE measured for different spectrum ranges demonstrate nonmonotonic behavior, which indicates the magnetic inhomogeneity of the layers. The peculiarities of the magneto-optical spectra of GaMnAs, which were not observed previously, were explained by taking the magnetic and phase inhomogeneity of the layers into account. The sensitivity of TKE to the phase inhomogeneity of the Ga(In)MnAs layers and the efficiency of TKE in studying the electron spectrum and magnetic structure of diluted magnetic superconductors are demonstrated.

Terahertz emission characteristics of GaMnAs dilute magnetic semiconductor under 650 mT external magnetic field

We investigate the effects of an externally applied magnetic field on the terahertz (THz) emission of Gallium Manganese Arsenide (GaMnAs) films grown via molecular beam epitaxy (MBE). Results show that low Mn-doping in GaMnAs resulted to increased THz emission as compared with a SI-GaAs substrate. Further increase in Mn-doping content resulted to a comparably less THz emission, which is attributed to reduced crystallinity and higher free-carrier absorption. Under an external magnetic field, the contributions of the Bup and Bdown-related THz emission were observed to be asymmetric: possibly due to intrinsic magnetic properties of GaMnAs.

Anisotropic magnetocapacitance in ferromagnetic-plate capacitors

The capacitance of a parallel plate capacitor can depend on applied magnetic field. Previous studies have identified capacitance changes induced via classical Lorentz force or spin-dependent Zeeman effects. Here we measure a magnetization direction dependent capacitance in parallel-plate capacitors where one plate is a ferromagnetic semiconductor, gallium manganese arsenide. This anisotropic magneto-capacitance is due to the anisotropy in the density of states dependent on the magnetization through the strong spin-orbit interaction.

Model for the Surface Anisotropy Field Observed in Spin-Wave Resonance in (Ga,Mn)As Thin Films

Dilute ferromagnetic semiconductors are a class of very promising materials of the future [1 6]. Gallium manganese arsenide (Ga,Mn)As, created on the basis of the semiconductor gallium arsenide by the addition of a small percentage of manganese as a magnetic dopant, is one of the most intensively studied compounds in this class [7 12]. Spin-wave resonance in thin lms has been studied particularly intensively in gallium manganese arsenide in the past decade [13 21]. Especially rich resonance spectra were obtained in studies with a variable con guration of the static eld with respect to the lm surface. The eld was rotated perpendicularly to the lm surface, which corresponds to variable polar angle θH between the direction of the external eld and the surface normal. In the present paper we shall analyze SWR measurement data concerning the out-of-plane rotation of the magnetic eld, mainly because of the controversy that arose in the interpretation of these results over an issue which therefore requires elucidation. If researchers tend to agree on the interpretation of SWR spectra in two extreme con gurations the perpendicular and parallel con gurations, corresponding to θH = 0 and θH = 90 ◦, respectively the interpretation of results obtained in intermediate con gurations is under debate. Almost as a rule, a particular con guration of the external eld tends to occur in this range at a critical angle θ H , for which the multi-peak SWR spectrum collapses to a single-peak FMR spectrum. There are two schools of thought regarding the interpretation of the occurrence of this critical angle. Both schools agree that in the critical con guration the thin lm is magnetically homogeneous, and the boundary conditions (speci cally, the surface spin pinning) correspond to the natural conditions, only resulting from the reduced neighborhood of the surface

Hidden order revealed

Dilute magnetic semiconductors such as gallium manganese arsenide could be key to the development of spintronics. But the relationship between electronic transport and magnetic properties has been hotly debated. Data indicating the preservation of the non-magnetic character of the host material provide startling new insight.

Lattice constant variation and complex formation in zincblende gallium manganese arsenide

We perform high resolution x-ray diffraction on GaMnAs mixed crystals as well as on GaMnAs/GaAs and GaAs/MnAs superlattices for samples grown by low-temperature molecular-beam epitaxy under different growth conditions. Although all samples are of high crystalline quality and show narrow rocking curve widths and pronounced finite thickness fringes, the lattice constant variation with increasing manganese concentration depends strongly on the growth conditions: For samples grown at substrate temperatures of 220 and 270 °C, the extrapolated relaxed lattice constant of Zincblende MnAs is 0.590 nm and 0.598 nm, respectively. This is in contrast to low-temperature GaAs, for which the lattice constant decreases with increasing substrate temperature.