Effect of Fe substitution on structural and magnetic properties of Pr 2

This work focuses on the synthesis, structure, and magnetic properties of Pr-Co-Fe compounds. Our previous study of Pr2Co7 alloys with high coercivity is shown that for samples annealed at Ta= 800 °C, the main phase is hexagonal of the Ce2Ni7 type structure. This leads to the formation of a magnetically hard Pr2Co7 phase; the coercivity being equal to 18 kOe at 293 K and 23 kOe at 10 K and important saturation magnetization. These performances are due to the combination of the complementary characteristics of 3d-itinerant and 4f-localized magnetism of Co and Pr, respectively. Its Curie temperature is about 600 K. The aim of this study is to follow the effect of partial substitution of Co by Fe on Pr2Co7-xFex structural and magnetic properties, where x =0.25, 0.50, 0.75 and 1. These compounds were synthesized by mechanical alloying. The Rietveld analysis of DRX shows that these intermetallics, annealed at Ta = 700 °C, adopt mainly hexagonal Ce2Ni7 type structure with P63/mmc group space. Moreover, it points out a lattice expansion along the c axis after Fe substitution for Co. Furthermore, these hexagonal phases possess magnetic properties more attractive than Pr2Co7, the Curie temperatures are higher than Pr2Co7 ones and the highest is obtained for x = 0.5 where TC = 760 K. This increase is due to the well-known electronic effect that invokes the reduction of antiferromagnetic coupling. These phases are particularly promising for permanent magnet applications

Effect of Fe substitution on structural and magnetic properties of Pr2Co7-xFex compounds

This work focuses on the synthesis, structure, and magnetic properties of Pr-Co-Fe compounds. Our previous study of Pr2Co7 alloys with high coercivity is shown that for samples annealed at Ta= 800 °C, the main phase is hexagonal of the Ce2Ni7 type structure. This leads to the formation of a magnetically hard Pr2Co7 phase; the coercivity being equal to 18 kOe at 293 K and 23 kOe at 10 K and important saturation magnetization. These performances are due to the combination of the complementary characteristics of 3d-itinerant and 4f-localized magnetism of Co and Pr, respectively. Its Curie temperature is about 600 K. The aim of this study is to follow the effect of partial substitution of Co by Fe on Pr2Co7-xFex structural and magnetic properties, where x =0.25, 0.50, 0.75 and 1. These compounds were synthesized by mechanical alloying. The Rietveld analysis of DRX shows that these intermetallics, annealed at Ta = 700 °C, adopt mainly hexagonal Ce2Ni7 type structure with P63/mmc group space. Moreover, it points out a lattice expansion along the c axis after Fe substitution for Co. Furthermore, these hexagonal phases possess magnetic properties more attractive than Pr2Co7, the Curie temperatures are higher than Pr2Co7 ones and the highest is obtained for x = 0.5 where TC = 760 K. This increase is due to the well-known electronic effect that invokes the reduction of antiferromagnetic coupling. These phases are particularly promising for permanent magnet applications

Consistently dated Atlantic sediment cores over the last 40 thousand years

Abstract: Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies

Do intertidal Zostera noltei meadows represent a favourable habitat for amphipods? The case of the Kneiss Islands (Gulf of Gabès: Central Mediterranean Sea)

International audienceThe structure, diversity, spatial and seasonal distributions of amphipod assemblages associated with intertidal Zostera (Zosterella) noltei meadows were studied around the Kneiss Islands (central Mediterranean Sea). This site represents a site of international interest in terms of its ornithological diversity (Important Bird Area, Ramsar Site and SPAMI). The amphipod fauna was sampled at 32 stations in spring 2014. A total of 6,482 individuals belonging to 78 species and 22 families were identified; among these taxa, Lysianassa ceratina is new for the Tunisian amphipod inventory, whereas 25 species are identified for the first time in the Gulf of Gabès. The dominant species are Cymadusa filosa, Microdeutopus gryllotalpa, Gammarus insensibilis, Dexamine spini-ventris, Monocorophium insidiosum, Elasmopus rapax, Melita palmata and Leucothoe incisa. Four amphipod assemblages are identified using MDS analysis. The distribu-tion of amphipod assemblages is linked to several environmental factors, such as sediment type, organic matter content and distance from the shore, which is itself associated with a clear inshore–offshore gradient. Seasonal variations of the amphi-pod assemblage patterns at eight stations, sampled between April 2014 and January 2015, show a maximum abundance and diversity during summer and autumn, with a minimum in winter. These seasonal fluctuations may be related to many factors such as variations of climatic factors (e.g. temperature, salinity), the growth and produc-tion rates of Zostera noltei meadows and seasonal patterns in the life cycle of domi-nant species