Anomalous Boson Behavior and Nanometric Heterogeneity in Glassy Fresnoite

In-situ observation of the boson peak, ω BP , of as-quenched and annealed glassy Ba 2 TiGe 2 O 8 (BTG) and Ba 2 TiSi 2 O 8 (BTS) was performed during a heating process. Although annealed glassy BTG and BTS indicated a monotonous decrease in ω BP with temperature, the as-quenched varieties, which included internal stress, revealed anomalous boson behavior at ∼600 °C, lower than each one's glass-transition temperature. It was suggested that the ω BP anomaly was caused by β-relaxation. This experimental result also supports the inhomogeneous structure (or cluster) model of glass.