ABSTRACT
Temperature treatment of magnetic Mn-Zn ferrites with the composition Mn0.6Zn0.2Fe2.2O4 up to 1100 °C results in a tremendous enhancement of the saturation magnetization by more than 60%. Employing a robust combined Rietveld refinement of powder X-ray and neutron diffraction (PXRD and NPD) data, it is revealed how a reordering of the cations takes place during the annealing step, the extent of which depends on the annealing temperature. While Zn(II) exclusively occupies tetrahedral sites throughout the whole temperature range, as the annealing temperature increases up to 700 °C, the Mn(II) cation distribution shifts from 80(7)% of the total Mn content occupying the octahedral sites (partly inverse spinel) to Mn only being present on the tetrahedral sites (normal spinel). Above 700 °C, pronounced crystallite growth is observed, followed by an increase of the saturation magnetization. Complementary techniques such as energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) confirm an even cation distribution and the particle growth with annealing temperature. The structural changes caused by annealing of spinel ferrites directly alter the magnetic properties of the materials, thus serving as an easy handle for enhancing their magnetic properties.
ABSTRACT
A mortality event at the Christiansø colony in the Baltic proper killed 115 common eiders (Somateria mollissima) in mid-May 2016. To complement previous studies of incubating females, 39 males were necropsied and from a subsample of these a biochemical and haematological profile was obtained. The birds were emaciated and cachexic having a 50% reduction in body mass. Twenty-nine eiders were diagnosed with hydropericardium, 15 had hunger edema, three birds had enteritis and a single air sac infection. All birds were infested with intestinal Polymorphus minutus and 32 of these with the intestinal Trematoda spp. Microscopic parasitic investigations identified endoparasitic trematodes of the families Bucephhalidae, Echinostomidae, Notocotyluridae and Levinsiniella. White blood cell count showed slight heterophilia and lymphopenia while the albumin:globulin ratio (0.28) indicated stress, immune supression and inflammatory reactions supported by a high heterophil:lymphocyte index (13). Declined plasma concentration of glucose, fructosamine, amylase, albumin and protein likewise indicated long-term starvation prior to mortality indicating phase III starvation (catabolism of protein). The dramatic increase in aspartate transaminase, glutamate-dehydrogenase, lactate-dehydrogenase and bile acids indicate liver disorders while dehydration, renal, heart and bone disorders was reflected in the increased uric acid, urea, phosphor and potassium values. These findings show that male eiders undergo long-term starvation and multi organ failure similar to that of incubating females previously reported from the same colony. It increases our knowledge of the physiology of starving eiders and add to our understanding of the recurrent mortality events in the colony that seems to be linked to changes in food availability being an important factor together with a warmer climate in a declining Baltic eider population. We recommend future studies to focus on food composition, migration patterns and environmental changes including parasitic infections and global warming.
