Inverse Melting of Polar Order in Chemically Substituted BaTiO_{3}

Area of Science:

• Condensed matter physics
• Materials science
• Crystallography

Background:

• Long-range order typically emerges in condensed matter systems at low temperatures.
• Some systems with competing interactions or quenched disorder exhibit inverse melting, becoming more disordered as temperature decreases.
• Ferroelectric oxides are crucial in electronic devices, and understanding their order-disorder transitions is vital.

Purpose of the Study:

• To investigate the phenomenon of inverse melting in a disordered ferroelectric oxide.
• To visualize the atomic-scale behavior of polar order in BaTi_{1-x}Zr_{x}O_{3} under varying temperatures.
• To understand the role of quenched chemical disorder in driving inverse melting.

Main Methods:

• In situ scanning transmission electron microscopy (STEM) for direct atomic-scale visualization.
• Synthesis and characterization of BaTi_{1-x}Zr_{x}O_{3} with quenched chemical disorder.
• Analysis of temperature-dependent structural and polar ordering.

Main Results:

• Observed inverse melting of polar order in BaTi_{1-x}Zr_{x}O_{3}, a departure from the parent BaTiO_{3} system.
• Demonstrated a reentrant disordered configuration at low temperatures, following an ordered state at intermediate temperatures.
• Linked the inverse melting to random fields generated by Zr dopants, influencing the balance between thermal fluctuations and pinning potentials.

Conclusions:

• Quenched chemical disorder can induce inverse melting in ferroelectric oxides.
• The interplay between thermal fluctuations and random fields governs the order-disorder landscape in such materials.
• Understanding inverse melting is crucial for designing advanced functional materials with tailored properties.