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Evidence of Spin Reorientation by Mössbauer Analysis
We report the crystallographic and magnetic properties of Ni0.3Fe0.7Ga2S4 by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a Mössbauer spectroscopy. In particular, Ni0.3Fe0.7Ga2S4 was studied by Mössbauer analysis for evidence of spin reorientation. The chalcogenide material Ni0.3Fe0.7Ga2S4 was fabricated by a direct reaction method. XRD analysis confirmed that Ni0.3Fe0.7Ga2S4 has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The Mössbauer spectra of Ni0.3Fe0.7Ga2S4 at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, EQ has anomalous twopoints of temperature dependence of EQ curve as freezing temperature, Tf = 11 K, and Néel temperature, TN = 26 K. This suggests that there appears to be a slowly-fluctuating “spin gel” state between Tf and TN, caused by non-paramagnetic spin state below TN. This comes from charge re-distribution due to spin-orientation above Tf , and TN, due to the changing EQ at various temperatures. Isomer shift value (0.7 mm/s ≤ δ ≤ 0.9 mm/s) shows
that the charge states are ferrous (Fe2+), for all temperature range. The Debye temperature for the octahedral site was found to be ΘD = 260 K.
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