Magnetic anomalies, chemical and magnetic properties at wide temperature range (15–1000 K) in LiSrxFe5-xO8 (x = 0, 0.025, 0.05)

Abstract

We report on magnetic anomalies at low temperatures, high Curie temperature values, structural and chemical properties of Sr doped LiFe5O8 bulk material. Micron size LiSrxFe5−xO8 (x = 0, 0.025, 0.05) are seen to crystallize in ordered α-LiFe5O8 phase with the space group of P4332. Chemical states of Li, Fe, Sr and O are confirmed from X-ray photoelectron spectroscopy measurements. Domain wall thickness is calculated to be 60 nm, 59.4 nm and 52.5 nm for x = 0, 0.025, 0.05 samples respectively. Field cooled (FC) and zero field cooled (ZFC) measurements from 300 K to 15 K shows several anomalies in LiSrxFe5−xO8 (x = 0, 0.025, 0.05) samples. Magnetic anomalies are observed at Tm1 (275 K), Tm2 (225 K), Tm3 (125 K), Tm4 (80 K) and Tm5 (30 K) for the pure LiFe5O8 sample and for the Sr doped samples, two sharp jumps in magnetization are observed around Tm6 (250 K) and Tm7 (75 K). Saturation magnetization and Curie temperature values are seen to decrease with the partial substitution of Sr2+ ions for the Fe3+ ions in α-LiFe5O8 structure. Remanent magnetization, magnetocrystalline anisotropy constant (K1) and coercivity values are seen to increase with increasing Sr concentration. LiSrxFe5−xO8 (x = 0, 0.025, 0.05) samples exhibit magnetic anomalies at low temperatures and exhibit hard magnetic behavior with Sr substitution.