Mossbauer and Density Functional Studies of Ferrimagnetic Fe3Se4

초록

Monoclinic Fe-3 Se-4 was synthesized using a ceramic method. M & ouml;ssbauer spectroscopy and density functional theory were used to investigate the physical origins of its ferrimagnetism and high coercivity. At 78 K, 12 M & ouml;ssbauer absorption lines were observed. These lines are composed of two subspectra, A and B, corresponding to Fe atoms at the 2 a and 4 i sites, respectively. At 320 K, the M & ouml;ssbauer spectrum collapsed, indicating a transition from a ferrimagnetic to a paramagnetic state. This temperature is close to the Curie temperature ( T-C ) of 331 or 315 K reported in the literature. The analysis of local structural symmetry confirmed that the Fe atoms in the 2 a sites are more symmetrically coordinated with neighboring Se atoms than those in the 4 i sites. Therefore, the Fe atoms in the 2 a sites exhibit a higher hyperfine magnetic field (HMF) of 225 kOe and a weaker quadrupole splitting (QS) of 0.17 mm/s than the Fe atoms in the 4 i sites, which exhibit an HMF of 105 kOe and a QS of 0.55 mm/s. Our density functional study confirmed that Fe-3 Se-4 exhibits ferrimagnetic behavior, with a magnetic moment of 4.48 mu (B) /u.c. and a T-C of 354 K. Fe (3) Se (4) shows a high magnetocrystalline anisotropy constant ( K-u ) of 0.9 x 10(6) erg/cm(3) . This high K-u value is attributed to the Fe atoms at the 4 i sites. It is suggested that the high coercivity of Fe-3 Se-4 , as reported in the literature, is due to the distorted 4 i site, which experiences the Jahn-Teller effect.

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