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摘要
Lattice dynamics in a sigma-Fe60V40 compound, which shows a re-entrant magnetism and orders ferromagnetic at T-C approximate to 170 K, was investigated with the Mossbauer spectroscopy in the temperature interval of 5300 K. Two relevant spectral parameters viz. the average center shift, < CS >, and the relative recoil-free fraction, f/f(o), were explored. The former yielded the Debye temperature, T-D1, and the mean-square velocity of vibration, < v(2)>, while the latter T-D2 and the mean-square amplitude of vibrations, < x(2)>. Significant differences in the lattice-dynamical behaviors in the magnetic and paramagnetic phases were revealed. In particular, the values of T-D were notably lower and those of f/f(o) greatly higher in the former. This anomalous result has likely its origin in a remarkably high anharmonic contribution to the vibrations found for the ground magnetic state (spin-glass). Especially anomalous behavior vs. temperature exhibits < x(2)> where four well defined ranges could have been identified and ascribed to the paramagnetic, ferromagnetic and two spin-glass phases. Linear correlations between < v(2)>-< x(2)> were found within each of the four ranges. They enabled determination of force constants, hence a change of the potential energy, E-p, in each of the ranges. The total change of E-p approximate to 30 meV while the corresponding one of the kinetic energy, determined from the knowledge of < v(2)>, was E-k approximate to 21 meV. The lack of balance between E-p and E-k follows from the anharmonic lattice-dynamical behavior observed in the spin-glass state. The results give a strong evidence that magnetism can significantly affect the lattice dynamics.
- 出版日期2017-11-1
