Increasing Magnetic Hardness of Fe3Se4 via Cu Doping

The influence of Cu doping on the structural and magnetic properties of the Fe3Se4 ferrimagnet has been investigated by a combination of X-ray diffraction, Raman spectroscopy, X-ray absorption spectroscopy, and magnetic measurements. While the effects of dopants with ionic radii closer to those of the Fe sites in Fe3Se4 had been studied before, Cu is a less conventional dopant, due to its smaller size (at the same ionic charge) and preference for lower coordination numbers. A (Fe1–xCux)3Se4 series, where x = 0–0.15, has been prepared by either high-temperature annealing or the solvothermal method. Although only a limited amount of Cu enters the Fe3Se4 structure, the Cu doping causes a substantial increase in the coercivity of the material. Furthermore, the samples prepared by the solvothermal method exhibit much larger coercive fields as compared to those observed for the samples prepared by high-temperature annealing. The effect was traced to the higher lattice strain accumulated in the samples synthesized solvothermally, as evidenced by the broadening of their Raman peaks.