Raman spectroscopic study of MnAl2O4 galaxite at various pressures and temperatures

The vibrational properties of synthetic galaxite, MnAl2O4, were investigated at various pressures (0-29.7 GPa) and temperatures (80-973 K), respectively. The Raman frequencies of all observed bands for galaxite continuously increase with increasing pressure and decrease with increasing temperature, respectively. The quantitative analysis shows that the lowest frequency T (2g) mode has the smallest isothermal mode Gruneisen parameter. Combined with previous studies, the thermal Gruneisen parameter of galaxite is determined to be 1.23(5). The quantitative analysis of temperature dependences of Raman bands yields that the lowest frequency T (2g) mode has the largest isobaric mode Gruneisen parameter. The intrinsic anharmonic mode parameters are also calculated and nonzero, indicating an existence of intrinsic anharmonicity for MnAl2O4 spinel.