Effect of polishing stress on Raman spectra of the Mn–Zn ferrite

Abstract

Raman scattering measurements were made on polycrystalline Mn0.62Zn0.30Fe2.08O4 ferrites with various degrees of stress generated during the polishing process, in the temperature range from 175 to 603 K. Raman spectra were found at energies of 337, 464, and 620 cm−1 in substrates with low stress. The integral intensities at 337 and 620 cm−1 increased significantly with decreasing residual stress stored in the surface. The former integral intensity remained constant with increasing temperature and decreased in the vicinity of the Néel point, while the latter one decreased linearly with increasing temperature through the Néel point. However, their linewidths changed little with stress and temperature, unlike the case of GaAs. These two spectra of the Mn–Zn ferrite, therefore, are considered to arise predominantly from the spin-dependent phonon scattering, in addition to the usual optical phonon scattering. It was thus found that the Raman intensity associated closely with the magnetic ordering is highly sensitive to the residual stress in the crystal, as in the case of the optical phonon, and Raman spectroscopy is also applicable to the evaluation of the stress in soft magnetic ferrites.