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Magnetic nanocrystalline Gd2O3 particles have been successfully synthesized in a silica glass matrix by the sol–gel method at calcination temperatures of 700 °C and above. The optical spectra, corresponding to the transition from ground 8S7/2 to the excited 6P, 6I and 6D multiplets, show a large blue shift which increases with decreasing particle size. Calculated free ion parameters represent different electrostatic and spin–orbit interactions of nanocrystalline Gd2O3 compared with the bulk Gd2O3. The thermal behaviour of magnetization (zero-field-cooled and field-cooled) and magnetic hysteresis of Gd2O3 nanocrystals in the 5–300 K temperature interval have demonstrated that the Gd2O3 nanocrystals present in these glasses display superparamagnetic–ferromagnetic transition at low temperatures. The present Gd2O3 nanoparticles embedded in the silica glass matrix show a high (∼103) dielectric constant with considerable low loss and good temperature-independent character associated with an important technological implication which promises wide applications in memory devices.

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The Physics of materials with large magnetoresistance (MR), defined as the percentage change of electrical resistance with the application of external magnetic field, has been an active field of research for quite some times. In addition to the fundamental interest, large MR has widespread application that includes the field of magnetic field sensor technology. New materials with large MR is interesting. However it is more appealing to vast scientific community if a method describe to achieve many fold enhancement of MR of already known materials. Our study on several manganite samples In present days science based society largely depends on several gadgets where magnetic field sensors play crucial role. The primary requirement for magnetoresistive sensor is the large magnetoresistance. Last two decades perovskite manganites was in the fore-front of the experimental research and resulted several thousand research articles with the primary focus on large magnetoresistance (MR). However, in manganites most of the cases large magnetoresistance occurs at very high (several tesla or more) magnetic field. The requirement of the large external magnetic field severely restrict the use of manganites as magnetic field sensor. Our findings in this manuscript show how the MR of the same material can be increased drastically even at the lower magnetic field.The doped perovskite manganite is generally represented by the formula R 1−x B x MnO 3 , where 'R' is a trivalent rare earth and 'B' is a bivalent element. Numerous fascinating properties of the doped manganites were observed depending on the bivalent element B and its doping concentration x. In addition to the metal-insulator transition and colossal magnetoresistance, doped manganite compounds usually show a generic phenomenon of charge ordering close to the doping concentrations x ~ 1 2 , 3 8 and some other concentrations. The charge-ordering (CO) is the real space ordering of the Mn 3+ and Mn 4+ ions and it is generally followed by an antiferromagnetic transition with the lowering of temperature. The high resistive insulating behavior with lowering the temperature below the charge-ordering transition temperature is also a generic behavior of the charge-ordered manganites. In the presence of external perturbations like magnetic field, electric field, x-ray irradiation etc., the high resistive insulating state transforms into a low resistive metallic state as a results of destabilization of the charge ordering. The magnetic field-induced destabilization of the charge ordering leads to the gigantic change of the resistance which is known as colossal magnetoresistance. The required magnetic field to destabilize the charge ordered state depends upon the electronic band width of the compounds and the charge-ordered state is more robust for lower band width system. During the last two decades, magnetoresistive properties of several doped perovskite manganites were extensively studied 1-8 . To consider manganites for technological purposes such as magnetic field sensor, the hi...

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