VP18-08 Crystallographic and Magnetic Properties of Manganese Ferrites Prepared by Liquid-Nitrogen Quenching
Creators: Sunghyun Yoon
Publisher: name: IEEE
Year: 2025

Structural and magnetic properties of Mn3-xFexO4 (0£x£2) has been studied by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. Polycrystalline Mn3-xFexO4 (0£x£2) samples were prepared by solid-state reaction method followed by sudden liquid nitrogen quenching. Room temperature XRD indicated a tetragonal to cubic structural transition across x=1 with the increase of x. Diffraction patterns showed a very dynamic shifts of peak positions as shown in Fig. 1; 2 or 3 peaks in the tetragonal realm have merged into single peak, and (105) and (312) diffraction peaks have even crossed each other. The lattice distortion can be explained by the Jahn-Teller effect of Mn3+ ions in the octahedral (B) site. Right of Fig. 1 shows the variations of the lattice constants and the tetragonality (c/a) with Fe substitution x. It is notable from GSAS refinement that tetragonal and cubic (~17 %) phases coexisted when x=1, which means FeMn2O4 is the marginal composition between cubic and tetragonal structures. Room-temperature M-H curves of the Mn3-xFexO4 (0x£2) are shown in Fig. 2. MS increases with Fe substitution x indicative of the occupancy of Fe3+ ions on the B site. When x=0.5 in the right of Fig. 2, paramagnetism and ferrimagnetism with MS»0.08 emu/g superimposed in the hysteresis curve and finally became paramagnetic when x=0. All the samples showed soft magnetic nature. Coercivity HC above x=0.5 were about 100 Oe, independent of composition. Mössbauer spectra showed asymmetric paramagnetic doublet below x=0.5 at room temperature. Since the room-temperature spectra for x≥1 also had overlap of thermally broadened magnetic sextets, we used the spectra taken at T=20 K in order to analyze the Fe cation distribution in the samples. All the cubic samples (x≥1) showed comparable absorption areas of the tetrahedral (A) and the B sites. Isomer shift of the sub-spectra indicated that all Fe ions were in ferric stare. Quadrupole splitting of the octahedral site increased as Fe ion content x decreased down below x=1. Spectral area ratio analysis reveals that there is significant amount of Fe3+ in the A site, which is in contrast to many reports that all the Mn2+ preferentially occupy the A site.
Structural and magnetic properties of Mn3-xFexO4 (0£x£2) has been studied by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. Polycrystalline Mn3-xFexO4 (0£x£2) samples were prepared by solid-state reaction method followed by sudden liquid nitrogen quenching. Room temperature XRD indicated a tetragonal to cubic structural transition across x=1 with the increase of x. Diffraction patterns showed a very dynamic shifts of peak positions as shown in Fig. 1; 2 or 3 peaks in the tetragonal realm have merged into single peak, and (105) and (312) diffraction peaks have even crossed each other. The lattice distortion can be explained by the Jahn-Teller effect of Mn3+ ions in the octahedral (B) site. Right of Fig. 1 shows the variations of the lattice constants and the tetragonality (c/a) with Fe substitution x. It is notable from GSAS refinement that tetragonal and cubic (~17 %) phases coexisted when x=1, which means FeMn2O4 is the marginal composition between cubic and tetragonal structures. Room-temperature M-H curves of the Mn3-xFexO4 (0x£2) are shown in Fig. 2. MS increases with Fe substitution x indicative of the occupancy of Fe3+ ions on the B site. When x=0.5 in the right of Fig. 2, paramagnetism and ferrimagnetism with MS»0.08 emu/g superimposed in the hysteresis curve and finally became paramagnetic when x=0. All the samples showed soft magnetic nature. Coercivity HC above x=0.5 were about 100 Oe, independent of composition. Mössbauer spectra showed asymmetric paramagnetic doublet below x=0.5 at room temperature. Since the room-temperature spectra for x≥1 also had overlap of thermally broadened magnetic sextets, we used the spectra taken at T=20 K in order to analyze the Fe cation distribution in the samples. All the cubic samples (x≥1) showed comparable absorption areas of the tetrahedral (A) and the B sites. Isomer shift of the sub-spectra indicated that all Fe ions were in ferric stare. Quadrupole splitting of the octahedral site increased as Fe ion content x decreased down below x=1. Spectral area ratio analysis reveals that there is significant amount of Fe3+ in the A site, which is in contrast to many reports that all the Mn2+ preferentially occupy the A site.