We report the synthesis of nominal 2 and 5 at.% Mn-doped ZnO nanocrystalline particles by a co-precipitation method. Rietveld refinement of x-ray diffraction data revealed that Mn-doped ZnO crystallizes in the monophasic wurtzite structure and the unit cell volume increases with increasing Mn concentration. DC magnetization measurements showed ferromagnetic ordering above room temperature with Hc∼150 Oe for nominal 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. A distinct ferromagnetic resonance (FMR) signal was observed in the EPR spectra of the 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. EPR measurements were used to estimate the number of spins participating in ferromagnetic ordering. Of the total Mn present in the 2 at.% Mn ZnO lattice, 25% of the Mn2+ ions were responsible for ferromagnetic ordering, whereas nearly 5% of the Mn2+ ions remained uncoupled (isolated spins). A well resolved EPR spectrum of 5% Mn-doped ZnO samples annealed at 875–1275 K (g = 2.007, A = 80 G, D = 210 G and E = 15 G) confirmed that Mn was substitutionally incorporated into the ZnO lattice as Mn2+. On increasing the temperature of annealing beyond 1075 K an impurity phase emerges in both the 2 and 5 at.% Mn-doped ZnO samples, which has been identified as a variant of (Zn1−XMn(II)X)Mn(III)2O4 with Tc∼15 K. Our results indicate that the observed room temperature ferromagnetism in Mn-doped ZnO can be attributed to the substitutional incorporation of Mn at Zn-sites rather than due to the formation of any metastable secondary phases.

La 2 NiMnO 6 (LNMO) was prepared by a combustion method followed by heating at high temperature. Subsequently, the preformed LNMO was annealed in air, oxygen, or N 2 atmosphere and characterized by powder x-ray diffraction (XRD), neutron diffraction, superconducting quantum interference device magnetometry, and dielectric analysis. Structural studies by XRD and neutron diffraction revealed the coexistence of partially cation disordered monoclinic (31%) and rhombohedral (69%) phases in the sample annealed in air. However, the sample annealed in oxygen shows about 50:50% of monoclinic and rhombohedral phases. Relaxor-like behavior with relative permittivity of the order of 10 4 was observed in the sample annealed in air, while relative permittivity decreases to about 200 in samples annealed in oxygen atmosphere. The magnetic properties indicate a well-defined ferromagnetic phase in the oxygen-annealed sample compared to a feeble ferromagnetic signature in the air-annealed one. The dielectric and ferromagnetism of LNMO samples have been related to formation and annihilation of oxygen vacancies.

In this study we report the synthesis of BiFeO(3) nanorods using a sonochemical technique. The nanorods had a diameter of 20-50 nm, a length of 100-500 nm and exhibit aspect ratios in the range of 5-10. However, after doping, the TEM images of Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) and Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO(3) nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M-H relationship reported for bulk BiFeO(3). The saturation magnetization of these BiFeO(3) nanostructures has been found to increase on doping with various metal ions (Ba(2+), Ca(2+), Mn(2+), Cr(3+)), reaching a maximum value of 1.35 emu g(-1) for the Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) nanostructures. However, saturation of electric polarization was observed only in case of the Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) nanostructures.

We report the preparation, characterization, and magnetic properties of highly crystalline colloidal Fe-doped indium oxide nanoparticles. The nanoparticles have been prepared in high yields by simple one-pot thermal decomposition of indium and iron precursors in hexadecylamine and can be easily dispersed in solvents like chloroform and toluene. Detailed X-ray diffraction, microstructure, and Raman studies reveal that the nanoparticles are single phase cubic bixbyite structure without any parasitic secondary phases. DC magnetization studies as a function of temperature and field indicate that nanoparticles are weakly ferromagnetic at room temperature (RT). This observation is further confirmed by the electron paramagnetic resonance spectra of the samples, which show a distinct ferromagnetic resonance signal at RT.