Observation of Mermin-Wagner behavior in LaFeO<sub>3</sub>/SrTiO<sub>3</sub> superlattices.
basic_science · Level V
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- Record sourced from PubMed, PMID 38906872.
- Also identified by DOI 10.1038/s41467-024-49518-0 and PMC identifier 11192889.
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Abstract
Two-dimensional magnetic materials can exhibit new magnetic properties due to the enhanced spin fluctuations that arise in reduced dimension. However, the suppression of the long-range magnetic order in two dimensions due to long-wavelength spin fluctuations, as suggested by the Mermin-Wagner theorem, has been questioned for finite-size laboratory samples. Here we study the magnetic properties of a dimensional crossover in superlattices composed of the antiferromagnetic LaFeO<sub>3</sub> and SrTiO<sub>3</sub> that, thanks to their large lateral size, allowed examination using a sensitive magnetic probe - muon spin rotation spectroscopy. We show that the iron electronic moments in superlattices with 3 and 2 monolayers of LaFeO<sub>3</sub> exhibit a static antiferromagnetic order. In contrast, in the superlattices with single LaFeO<sub>3</sub> monolayer, the moments do not order and fluctuate to the lowest measured temperature as expected from the Mermin-Wagner theorem. Our work shows how dimensionality can be used to tune the magnetic properties of ultrathin films.