Raman spectroscopic study of MnAl 2 O 4 galaxite at various pressures and temperatures

The vibrational properties of synthetic galaxite, MnAl 2 O 4 , 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 2 g mode has the smallest isothermal mode Grüneisen parameter. Combined with previous studies, the thermal Grüneisen 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 2 g mode has the largest isobaric mode Grüneisen parameter. The intrinsic anharmonic mode parameters are also calculated and nonzero, indicating an existence of intrinsic anharmonicity for MnAl 2 O 4 spinel.