الفهرس 
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Abstract
The Mn-Cr ferrite doped with some rare earth is investigated to probe its compatibility as an optical detector. The prepared sample has the general formula MnCrxRyFe2-x-y04, where R is the rare earth metal ion R = {Gd, Srn, Ce, Dy and La}. IR and X-ray spectra of the prepared samples have been carried out to confirm spine! structure formation. Raman spectra of the samples showed that X-Ray and IR results are verified. The five appeared active Raman band confirms the space group of the ferrite as F 43m, and so the photo Galvano-Magnetic effect for the sample could be measured to investigate the resonance phenomena that could occur when illuminated with certain laser wavelength. The samples are prepared by the double sintering technique. The pure Mn-Cr ferrite of the general formula MnCrxFe2-x04, are first prepared at four different heating rates (1, 2, 4, and 6 eg./min) and final sintering at 1200 QC for 10 hours the real and imaginary parts of the samples are measured as a function of frequency and temperature. It has been found that, the critical was rate 4°C/min. The activation energy for this rate has been calculated which showed that the critical Cr3+ ion concentration for this compound was x = 0.5. The See beck coefficient for this rate has been carried out and it was found that, the charge is mainly ”holes”. Due to high polarization and high conductivity of the samples at the critical concentration, the La3+ ion as well as the rest of the rare earth are doped at that Cr concentration and prepared at that heating rate. The real and imaginary parts of the dielectric constant has been measured and the activation energy was calculated the results showed that the conductivity data for different samples showed that, the critical rare earth concentration was y = 0.02 at which maximum polarization takes place in the samples. At that rare earth critical concentration the other rare earth elements are doped are doped in the rest of the samples The general formula is then MnCr0.5R0.02Fe1.4804 where R = Gd, Ce, Dy and Sm. The dielectric constant and conductivity of the samples are studied. The maximum conductivity was found for the Gd doped samples. The Photo Galvano- Magnetic effect for the rare earth samples has been measured and the values of the cyclotron resonance, hopping resonance, and plasma resonance are reported for all samples. The best results that make ferrite as an optical detector are found for Gd doped sample. This result is enhanced by the results obtained from the photoconductivity of the sample, the highest emf values are found for Gd sample and the peak values at which the maximum photo current are reported. The calculated values for quantum efficiency and responsivty of the sample are also reported which has its maximum for Gd doped sample. The magneto impedance has also been measured for the rare earth samples and it was found that, the DROP in the impedance of Gd doped sample reaches 55٪which is the highest value with respect to the other samples. The thin film of the this sample has been prepared by pulsed laser technique, using Nd-Yag of wavelength 1064 nm, of out put of 120mJ and repetion rate of 10Hz the duration time at which the deposition takes place is one hours. The deposition is done on a quartz substrate of dimension 1.5x2 cm. The dielectric properties of the samples has been measured and compared with the bulk form. The real and imaginary parts of the dielectric constant peak position was found to shifts to higher temperature. The absorption and transmission spectra of the thin film has been carried out and it is found that the maximum absorbance occurs below 500 nm. The dielectric constant (real and imaginary parts) are calculated from the optical spectrum and compared to those obtained from the electrical measurements. The photoconductivity of the thin film sample showed that three peaks in the curve describes 3-wavelength regions at which maximum emf output takes place. The proper detector layer thickness at that three bands are calculated and it was found that it is in the range of 1.5up 2.7).1m. The responsivity and the quantum efficiency are also tabulated. The magneto impedance and Photo Galvano-Magnetic effect are a measured for the thin film sample and the resonance frequency are tabulated.