The Crystal Structures And Magnetoelectric Properties Of Double Perovskites Sr_2-xBa_xFe MoO_6-yN_y And Ca_2-xLa_xFe MoO_6-yN_y Series

The A-doped and O-doped compounds with double perovskite structure were synthesized by ammonolysis method and were characterized by means of X-ray diffraction,magnetic and electrical resistivity measurements.The effect of dopant on the crystal structure,magnetic properties and electrical behavior were studied.The result of Fullprof_suite refinement shows that the structure of Sr_2-xBa_x FeMoO_6-y N_y which tolerance factor is one are assigned to tetragonal system with space group I4/mmm and their cell parameters increase with ammonolysis time.At room temperature the isothermal magnetization,M-H,shows that the magnetization rapidly increases with external field,and then saturates to a value of MS.Thermal magnetization demonstrates that the metamagnetic transition temperature is above 450 K.Each sample shows a significant?-?magnoresistance in a 1.0 T magnetic field.For samples of ammonolysis 0,1,3 and 5 h,the resistivity in zero and 1.0 T magnetic fields reduces with temperature decreasing from 450 to 80 K,indicating that the sample exhibits metallic behavior in this temperature range.Whereas,the resistivity in zero magnetic field increases with temperature lowering from 250 to 80 K for ammonolysis 7 h,indicating that the sample demonstrates semiconducting-like behavior in this temperature range.Meanwhile,significant magnetoresistance?-??-0.1053?can be observed over sample of ammonolysis 7 h under 1.0 T magnetic field around room temperature.The result of Fullprof_suite refinement shows that the structure of Ca_2-x La_x FeMoO_6-y N_y are assigned to monoclinic system with space group P21/n and their cell parameters and bond angles increase with ammonolysis time.At room temperature the isothermal magnetization,M-H,shows that the magnetization rapidly increases with external field,but not saturates to a value of MS.Thermal magnetization demonstrates that the metamagnetic transition temperature is above 450 K.The resistivity in zero and 1.0 T magnetic fields reduces with temperature decreasing from 450 to 80 K for ammonolysis 1,3 and 5 h,indicating that the sample exhibits metallic behavior in this temperature range.Whereas,the resistivity in zero and 1.0 T magnetic fields increases with temperature from 450 to 80 K for ammonolysis 7 h,indicating that the sample demonstrates semiconducting-like behavior in this temperature range.