Crystalline InMnAs quantum dots with symmetric single spin domain particles have been formed on GaAs substrates using molecular beam epitaxy. The structural and magnetic properties of the quantum dots are characterized by a variety of techniques. Their magnetization curve as a function of temperature indicates that the ferromagnetic transition temperature is as high as 400 K (see Figure).

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the acute problem of eutrophication increasing in the environment is due to the increase of industrial wastewater, synthetic nitrogen, urine, and urea. this pollutes groundwater, soil and creates a danger to aquatic life. therefore, it is advantageous to use these waste materials in the form of urea as fuel to generate power using Microbial fuel cell (Mfc). in this work, we studied the compost soil Mfc(cSMfc) unlike typical Mfc with urea from the compost as fuel and graphite as a functional electrode. the electrochemical techniques such as cyclic Voltammetry, chronoamperometry are used to characterise CSMFC. It is observed that the CSMFC in which the compost consists of urea concertation of 0.5 g/ml produces maximum power. Moreover, iV measurement is carried out using polarization curves in order to study its sustainability and scalability. Bacterial studies were also playing a significant role in power generation. the sustainability study revealed that urea is consumed in cSMfc to generate power. this study confirmed that urea has a profound effect on the power generation from the CSMFC. Our focus is to get power from the soil processes in future by using waste like urine, industrial wastewater, which contains much amount of urea. The rapid increase in power consumption and various environmental issues have compelled the research community to identify new sources of renewable energy. It is pertinent to discover new renewable resources 1,4. In this pursuit, energy storage devices such as fuel cells, which are mostly powered by organic compounds, can be useful tools. Urea Fuel cells available in the liquid state are not sustainable and portable 1. However, in soil-based Microbial Fuel Cell (MFC) use natural bacteria or secreted enzymes to break down the fuel, typically to generate electricity from the soil. In MFCs, bacteria and enzymes to act as biocatalysts to produce electricity 1,2. Until now the reported liquid state MFCs associated with safety concerns mainly related to toxicity, shifting, leakage, handling and degrading fastly in the liquid state. Moreover, additional precautions are needed to prevent exposure to gaseous NH 3 due to volatilisation of the liquid fuel. Therefore, the solid-state materials like soil compost are preferred to overcome the risk, as mentioned above for stable behaviour. Among element of urine, urea is a suitable fuel for MFCs. It is an advantage for the soil-based system to go through the natural processes by following nitrification and denitrification in the nitrogen cycle by ammonification to nitrogen (N 2) formation in soil 3. The soil itself is a source of many bacteria and microorganisms in aerobic and anaerobic forms 4-8. Urea and ammonium are sources of nitrogen, and the density of urea is higher as compared to other nitrogen sources 2,3,9. Urea when comes in contact with the soil while hydrolysis releases urease enzymes working as a catalyst with bacteria. Therefore, soil systems can be a neutral medium to transport electrons and protons easily in an eco-friendly medium fo...

Achievement of a spin polarization without magnetic field through a GaMnN based ferromagnetic resonant tunneling diode (RTD) is proposed theoretically. The influences of the temperature and structure on the spin polarization current and differential conductance have been investigated. The clear spin splitting current can be observed in an optimal RTD structure without magnetic field even though the splitting energy of the ferromagnetic barrier is very small. Large spin polarization can be obtained and the polarization orientation can be varied by an applied bias voltage without external magnetic field.

We have investigated the effect of doping by Te on the anomalous Hall effect in Ga 1-

Zinc-blende structured MnAs epiaxial films with half metallic characteristics were grown on GaAs (100) substrates. The formation of the zinc-blende structured MnAs on GaAs was made possible via introduction of a strained yet epirelated InAs intermediate layer, the thickness of which was found critical for enabling the half metallic structure. The magnetization curves as functions of the magnetic fields showed magnetic hysteresis and isotropic ferromagnetic properties. The magnetoresistance behavior at various temperatures indicates that the MnAs thin film is half-metallic in nature.

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The effects of Mn delta-doping on the magnetic properties of (Ga1−xMnx)N thin films grown on GaN buffer layers by molecular-beam epitaxy were studied. The magnetization curve as a function of the magnetic field as 5K indicated that ferromagnetisms existed in the Mn delta-doped (Ga1−xMnx)N and (Ga1−xMnx)N thin films and that the magnetization in the Mn delta-doped (Ga1−xMnx)N thin film was significantly enhanced. The magnetization curve as a function of the temperature showed that the Curie temperature of the Mn delta-doped (Ga1−xMnx)N thin film was estimated to be above room temperature. The increase of the magnetization in the Mn delta-doped (Ga1−xMnx)N thin film in comparison with that in the (Ga1−xMnx)N thin film was attributed to the enhancement of the carrier-mediated ferromagnetism due to increased hole concentrations. The theoretical results showed that Ga vacancies near the Mn delta-doping layer were likely to cause p-type conductance, indicating that the enhancement of the magnetic properties in (Ga1−xMnx)N thin films originated from Mn delta doping.