In Mn1−xZnxFe2O4 (x=0 to 1) nanosize particles prepared through hydrothermal precipitation we observe a decrease in particle size from 13 to 4 nm with increasing Zn concentration from 0 to 1. The lattice constant, a, for all Mn/Zn concentrations is found to be less than that for the corresponding bulk values. At specific compositions within x=0.35 and 0.5, the temperature dependence of the magnetization exhibits a cusp-like behavior below the temperature at which the nanoparticles undergo a ferri- to para-magnetic transition (Tc). The Curie temperatures, Tc, of the nanoparticles are in the range of 175–500 °C, which are much higher than their corresponding bulk values. To explain these unusual features, the strong preferential occupancy of cations in chemically inequivalent A and B sites and the metastable cation distribution in nanoparticles are invoked.

No abstract

No abstract

No abstract

Direct detection of magnon spin transport by the inverse spin Hall effect Appl. Phys. Lett. 100, 082405 (2012) Ferromagnetic resonance of micro-and nano-sized hexagonal ferrite powders at millimeter waves J. Appl. Phys. 111, 07E113 (2012) Tuning the cation distribution and magnetic properties of single phase nanocrystalline Dy3Fe5O12 garnet J. Appl. Phys. 111, 07A517 (2012) Evolution of crystallographic texture and magnetic properties of polycrystalline barium ferrite thick films with Bi2O3 additive J. Appl. Phys. 111, 07A511 (2012) Field-induced magnetic transition in cobalt-ferrite J. Appl. Phys. 111, 07E308 (2012) Additional information on J. Appl. Phys. with xϭ0.32 were rf sputter deposited on fused quartz substrates at ambient temperature. The as-deposited films were found by x-ray diffraction to be amorphous but magnetic, and showed large high field susceptibility. The films were studied after they were annealed at various temperatures up to 850°C. It was observed that the films crystallize upon annealing and the value of the saturation magnetization increases with annealing temperature. The high field susceptibility, on the other hand, decreases with increasing anneal temperature. The measured ferromagnetic resonance spectra of these films indicated that the films consist of at least two different magnetic materials. A significant portion in the film crystallizes and the value of saturation magnetization of this portion tends to the bulk value as annealing temperature is increased. However, a small portion of the film remains in a highly defective state all through, even up to annealing temperatures of 850°C. The high field susceptibility data indicates that point defects could play an important role in determining the magnetic properties of these films.