Local inhomogeneous state in multiferroic SmCrO₃.

Area of Science:

• Solid State Physics
• Materials Science
• Crystallography

Background:

• Rare-earth orthochromites (RCrO3) with distorted perovskite structures exhibit debated ferroelectric order origins.
• The question of whether these materials are magnetically driven improper ferroelectrics, similar to rare-earth manganites and orthoferrites, remains a key research area.

Purpose of the Study:

• To investigate the atomic-scale behavior of samarium chromium oxide (SmCrO3) to elucidate the origin of its ferroelectric order.
• To determine if the ferroelectric phase in SmCrO3 arises from a simple structural transition or a more complex phenomenon.

Main Methods:

• Atomic-scale study of the samarium chromium oxide (SmCrO3) system.
• Electric Field Gradient (EFG) measurements.
• First-principles calculations.

Main Results:

• A distortion of the samarium (Sm) local environment emerges near room temperature within the paramagnetic phase.
• The observed emergent phase in SmCrO3 is not consistent with the previously reported Pna21 structure.
• A local inhomogeneous state, characterized by the coexistence of regular non-polar and polar distorted environments, develops at low temperatures.

Conclusions:

• The ferroelectric order in SmCrO3 does not stem from a simple structural phase transition to a Pna21 structure.
• A complex, low-temperature inhomogeneous state with coexisting polar and non-polar environments is responsible for the observed phenomena.
• This finding challenges existing models for ferroelectricity in rare-earth orthochromites.