Linear and nonlinear dielectric spectroscopy in dipolar glasses

Abstract

Two dipolar glass systems are investigated by broadband dielectric spectroscopy. The two systems under investigation, NH₄I:KI and solid solutions of deuterated betaine phosphate and betaine phosphite (BP: BPI), reveal very different freezing scenarios. The dielectric loss in NH₄I:KI is characterized by a power-law behavior on frequency ε′′ v′ ν^s , indicative for the near-equilibrium dynamics in the glass phase. The deuterated proton glass D-BP:BPI (40:60) exhibits a relaxational-type of freezing transition. Measurements of the nonlinear susceptibility and of the field cooled and zero-field cooled susceptibility provide clear evidence for a “static” dipolar glass transition at T_g ∼ 28 K ± 2 K.

Keywords:

• Orientational glasses
• dielectric spectroscopy
• nonlinear dipolar susceptibility