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Abstract
Two anomalous behaviors are observed in the Raman spectra of BaMnF4 at room temperature. One is that the number of Raman lines is smaller than that expected for the orthorhombic crystal structure with C 2ν 12 symmetry, the other is that, of the b(aa)c, a(bb)c, and b(cc)a scattering geometries giving the same A1-symmetry spectrum, the number of Raman lines in the b(aa)c spectrum is considerably smaller than those in the other two spectra. It is suggested that rotation of MnF6 octahedra about c-axis occurring in the orthorhombic phase is responsible for the former behavior, and Ba2+-ion displacement along a-axis for the latter one.