Narrow Results

Inserted narrow InAs quantum wells in InAs/InGaAs/InAlAs heterostructures have been used to achieve higher mobility for high-electron-mobility transistors (HEMTs) with ultra-low-power and low-noise amplification characteristics and for spin-based devices. Due to the large nonparabolicity of the conduction band of InAs and the penetration of the confined electronic envelope function into the adjacent layer(s), accurate calculations of effective mass and g-factor of charge carriers can be problematic. Methods of making precise determinations of the mass and other electronic parameters are thus of interest. We have applied magneto-photoresponse and -transmissions measurements at several THz laser frequencies in concert with dc magnetotransport measurements at low temperature (T = 1.6 K) to determine various electronic parameters (effective mass, carrier density, g-factor, mobility and the quantum scattering time) of the 2DEG in an InAs/In_0.75Ga_0.25As/In_0.75Al_0.25As inserted channel structure. This characterization method can also be used to probe the effect of strain, Rashba field, etc on the properties of charge carriers in such structures.

Here we present the results of magneto resistance measurements in tilted magnetic field and compare them with calculations. The comparison between calculated and measured spectra for the case of perpendicular fields enable us to estimate the dependence of the valley splitting as a function of the magnetic field and the total Landé g-factor (which is assumed to be independent of the magnetic field). Since both the exchange contribution to the Zeeman splitting as well as the valley splitting are properties associated with the 2D quantum confinement, they depend only on the perpendicular component of the magnetic field, while the bare Zeeman splitting depends on the total magnetic field. This information aided by the comparison between experimental and calculated gray scale maps permits to obtain separately the values of the exchange and the bare contribution to the g-factor.

This paper focuses on the synthesis and structural, optical, and magnetic characterization of Mn-doped CoFe₂O₄ nanoparticles synthesized by a simple chemical co-precipitation method. Synthesized magnetic nanoparticles were characterized by XRD, FTIR, UV-Vis, PL, TEM, VSM, and EPR spectroscopy. XRD analysis confirmed the significant reduction in the crystallite size from $\sim 17$nm to 10nm as the Mn content is increased from 0 to 1. UV-Vis spectra confirmed that the Co–Mn ferrite is a direct bandgap magnetic material that possesses an energy gap from 3.92eV to 4.33eV. FTIR vibrational frequency observed between 468 and 548 ${\text{cm}}^{-1}$confirmed the existence of metal–oxygen bond at tetrahedral and octahedral sites. Photoluminescence spectra confirmed the red emission of the samples from the peak at 680nm. TEM analysis suggests that the single domain of CoFe₂O₄ nanoparticles may vary between 38 and 72nm. Composition analysis confirmed the homogeneous mixing of Co, Mn Fe, and O atoms in the synthesized samples. The VSM study confirmed that Mn substitution favors transition from ferromagnetic to superparamagnetic. VSM analysis also confirmed the lessening in saturation magnetization and coercivity on Mn doping. The X-band electron paramagnetic resonance spectrum recorded at room temperature conveys that the superexchange interaction is increased with the increase in Mn concentration.

Triple coincidences between prompt γ-rays emitted in the spontaneous fission of ²⁵²Cf were measured with Gammasphere. These data are used to measure the angular correlation of cascades of γ-rays from excited states of neutron rich fission fragments stopped in an unmagnetized iron foil. The hyperfine fields in the iron lattice cause attenuations of the angular correlations between γ rays emitted from the excited states which have sufficiently long lifetimes. This attenuation is measured and used to calculate the g-factors of excited states in many neutron rich nuclei.

The rotational structures of ^256,257Rf are investigated by the particle-number-projected Cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) model. The experimental energies of the yrast bands are well reproduced within 0.5 MeV. The electromagnetic properties with the CNSB model for ²⁵⁶Rf generally agree with the projected shell model results. The calculated g-factor for ²⁵⁷Rf increases with the increasing spin and approaches the value of ²⁵⁶Rf for I ≳ 20. The resulted theoretical |(g_K − g_R)/Q₀| values in ²⁵⁷Rf are in agreement of available experimental data.

Inserted narrow InAs quantum wells in InAs/InGaAs/InAlAs hetrostructures have been used to achieve higher mobility for high-electron-mobility transistors (HEMTs) with ultra-low-power and low-noise amplification characteristics and for spin-based devices. Due to the large nonparabolicity of the conduction band of InAs and the penetration of the confined electronic envelope function into the adjacent layer(s), accurate calculations of effective mass and g-factor of charge carriers can be problematic. Methods of making precise determinations of the mass and other electronic parameters are thus of interest. We have applied magneto-photoresponse and -transmissions measurements at several THz laser frequencies in concert with dc magnetotransport measurements at low temperature (T = 1.6 K) to determine various electronic parameters (effective mass, carrier density, g-factor, mobility and the quantum scattering time) of the 2DEG in an InAs/In_0.75Ga_0.25As/In_0.75Al_0.25As inserted channel structure. This characterization method can also be used to probe the effect of strain, Rashba field, etc on the properties of charge carriers in such structures.