Study of disorder effects in La substituted Ca2FeMoO6 ferrimagnet using magnetic and transport measurements

Disorder induced magnetism and electrical conduction in La doped Ca2FeMoO6 double perovskite

“…On the other hand, the coercivity ͑H C ͒ increases from ϳ33 Oe for x = 0 sample to ϳ168 Oe for x = 0.7 sample. This indicates increasing magnetic hardness by La doping and consistent with the results at 5 K. 12 Since ferromagnetic order still retained for La doping up to x = 0.7, the increasing magnetic hardness could be related to increasing disorder or lattice defects either at grain boundary or inside the grains. 22…”

“…In the previous work 12 we noted soft ferromagnetic nature of the samples from field dependent magnetization M͑H͒ at 5 K. The spontaneous magnetic moment showed a gradual decrease upon La doping. The soft ferromagnetic nature of the samples is further confirmed from the field M͑H͒ curves at 300 K ͑Fig.…”

“…The decrease in magnetic irreversibility reflects the magnetic dilution effect on cluster glass phase coexisting with long ranged ferromagnetic order. 12 The peak behavior of MZFC͑T͒ curve for x = 0 sample is suppressed by increasing magnetic field to 500 and 5 kOe Fig. 1͑b͔͒.…”

“…Details have been reported earlier. 12 Stoichiometric amounts of high purity ͑Ͼ99.99%͒ La 2 O 3 , CaCO 3 , Fe 2 O 3 , MoO 3 , and Mo powders have been mixed and ground for 2 h. The La 2 O 3 has been pre-fired at around 950-1000°C for 12 h. The pellet form of the ground powder has been sintered in the temperature range 1000-1270°C in reducing atmosphere ͓flow of Ar/ H 2 ͑9:1͒ gas mixture͔. Single phased monoclinic structure with space group P2 I / n was confirmed from the x-ray diffraction spectrum of various compositions of La x Ca 2−x FeMoO 6 .…”

“…4,5,9,10 dc magnetization data may not reveal small disorder effect 11 but ac susceptibility and conductivity measurements are extremely useful for identifying disorder effects in double perovskite structure. 11,12 The transformation of metallic to nonmetallic conductivity at low temperature regime is related to the intrinsic disorder in double perovskite structure. 6,9,10,13,14 Nonmagnetic substitution in double perovskite structure ͑A 2 FeMoO 6 ͒ has opened another window to realize disorder effect.…”