Strain-induced high-temperature perovskite ferromagnetic insulator.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Ferromagnetic insulators are crucial for advanced magnetic devices like spintronic applications and magnetic tunneling junctions.
• Existing ferromagnetic insulators often have low-symmetry structures, hindering integration and leading to poor material properties.
• High-symmetry ferromagnetic insulators are scarce, with known materials exhibiting very low Curie temperatures or requiring chemical doping.

Purpose of the Study:

• To investigate the potential of LaCoO3 single-crystalline thin films under tensile strain as a high-performance ferromagnetic insulator.
• To explore the mechanism of strain-induced ferromagnetism in LaCoO3 and its dependence on stoichiometry.
• To assess the feasibility of achieving high transition temperatures suitable for practical applications.

Main Methods:

• Synthesis of LaCoO3 single-crystalline thin films subjected to tensile strain.
• Experimental characterization of magnetic properties, including Curie temperature (Tc) measurements.
• First-principles calculations to elucidate the underlying physics of strain-induced ferromagnetism and defect effects.

Main Results:

• Tensile strain induces ferromagnetism in LaCoO3, a property absent in the bulk material.
• A remarkably high Curie temperature (Tc) of up to 90 K was achieved in the strained, undoped LaCoO3 thin film.
• Ferromagnetism is strongly dependent on stoichiometry, diminishing significantly with increasing Co2+ defect concentration.

Conclusions:

• LaCoO3 thin films under tensile strain represent a rare, undoped perovskite ferromagnetic insulator with a high transition temperature.
• The study successfully demonstrates strain engineering as a viable route to achieve ferromagnetism above liquid-nitrogen temperatures.
• This material holds significant potential for integration into large-area device fabrication for next-generation spintronic technologies.