In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

ZnS nanostructures: From synthesis to applications

CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

CeO2 is a catalytic material of exceptional technological importance, and the precise role of oxygen vacancies is crucial to the greater understanding of these oxide materials. In this work, two ceria nanorod samples with different types and distributions of oxygen vacancies were synthesized. A direct relationship between the concentration of the larger size oxygen vacancy clusters and the reducibility/reactivity of nanosized ceria was revealed. These results may be an important step in understanding and designing active sites at the surface of metal oxide catalytic materials.

Oxygen Vacancy Clusters Promoting Reducibility and Activity of Ceria Nanorods

ZnO nanostructures for optoelectronics: Material properties and device applications

Positron annihilation spectroscopic characterization of defects in wide band gap oxide semiconductors

Differently heat treated and 55 MeV Li3+ beam irradiated Bi2Sr2Ca1Cu2O8+δ (Bi-2212) high temperature superconductors have been studied from the analysis of resistivity in the normal state as well as near the superconducting transition. For all the unirradiated and irradiated samples the so-called linear temperature dependence of the normal state resistivity, in a wide temperature range, can well be understood within the variable range hopping (VRH) conduction scenario. Near and above the bulk superconducting transition, the fluctuation enhanced conductivity (paraconductivity) analysis shows a noteworthy modification of the conduction process due to radiation induced defects.

Interesting aspects of the analysis of resistivity in Li3+ irradiated Bi-2212

Positron annihilation technique is a well known technique to characterize the defects in a material. These defects can be identified by positron annihilation lifetime and coincidence Doppler broadening of positron annihilation radiation measurement. In this chapter we report the room temperature positron annihilation lifetime for single crystalline ZnO. From our study it is confirmed that the present crystal contains VZn–hydrogen complexes with low open volumes. Another important nuclear solid technique is the Mossbauer Spectroscopic technique which has been used to probe the local magnetic properties of a solid. Here we have summarized Mossbauer spectroscopic studies on ferrites.

Probing Materials by Positron Annihilation Technique and Mossbauer Spectroscopy - Review

Doppler broadening of the electron positron annihilation γ-radiation spectra of single crystalline Bi2Sr2CaCu2O8+δ high Tc superconducting sample along the two different crystallographic orientations (c-axis and a–b-plane) have been analyzed by constructing ratio-curves with the reference spectra of defect free 99.9999% pure Al and Cu, respectively. The results indicate that the momentum component (pL) of the 2p electrons of oxygen ions and the 3d electrons of the Cu ions is relatively more towards the c-axis than the a–b-plane.

Doppler broadening measurements of positron annihilation in single crystalline Bi2Sr2CaCu2O8+δ high Tc superconductor along two different crystallographic directions

The effects of quenched disorder on the structural, transport and magnetic properties of the La0.7Ca0.3MnO3-type colossal magnetoresistive (CMR) sample have been reported. Temperature-dependent resistivity and magnetization data of the quenched sample revealed interesting changes from those of the usual slow-cooled sample. This is attributed to the defects created in the quenched sample and confirmed from the X-ray diffraction (XRD) and positron annihilation spectroscopic studies.

Anindya Sarkar

Papers

Positron annihilation spectroscopic characterization of defects in wide band gap oxide semiconductors

Interesting aspects of the analysis of resistivity in Li3+ irradiated Bi-2212

Probing Materials by Positron Annihilation Technique and Mossbauer Spectroscopy - Review

Doppler broadening measurements of positron annihilation in single crystalline Bi2Sr2CaCu2O8+δ high Tc superconductor along two different crystallographic directions

Studies of quenched disorder in La0.7Ca0.3MnO3-type CMR manganite system from magnetic, transport and positron annihilation spectroscopic measurements