Spin ice Thin Film: Surface Ordering, Emergent Square ice, and Strain Effects

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Recent experimental realizations of Dy$_{2}$Ti$_{2}$O$_{7}$ and Ho$_{2}$Ti$_{2}$O$_{7}$ spin ice thin films.
• The physics of confined gauge fields and emergent phenomena in magnetic materials.

Purpose of the Study:

• Investigate surface ordering in model spin ice thin films with [001] surfaces.
• Explore the stabilization of novel magnetic phases, such as square ice, in confined geometries.
• Understand the influence of strain on the magnetic properties and entropy of spin ice films.

Main Methods:

• Computational modeling of spin ice thin films.
• Analysis of dipolar interactions and surface bond inequivalence.
• Simulations to study phase transitions and temperature-dependent ordering.

Main Results:

• Open boundaries induce inequivalent 'orphan' bonds on surfaces.
• Tuning orphan bonds leads to 2D crystallization of magnetic surface charges.
• Stabilization of a square ice phase in single-unit-cell films.
• Ordering analogous to the 6-vertex model's F transition at lower temperatures.
• Strain effects qualitatively reproduce experimental observations of entropy loss.

Conclusions:

• Surface effects in spin ice thin films can drive novel magnetic ordering.
• Confined geometries offer pathways to engineer magnetic phases.
• Strain plays a crucial role in the low-temperature behavior of spin ice films, impacting their entropy.