Controlling 4f antiferromagnetic dynamics via itinerant electronic susceptibility

Optical manipulation of magnetism holds promise for future ultrafast spintronics, especially with lanthanides and their huge, localized <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mn>4</a:mn><a:mi>f</a:mi></a:math> magnetic moments. These moments interact indirectly by spin polarizing the conduction electrons (the Ruderman-Kittel-Kasuya-Yosida exchange interaction), influenced by interatomic orbital overlap, and the conduction electron's susceptibility around the Fermi level. Here, we study this influence in a series of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mn>4</b:mn><b:mi>f</b:mi></b:math> antiferromagnets, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>Gd</c:mi><c:msub><c:mi>T</c:mi><c:mn>2</c:mn></c:msub><c:msub><c:mi>Si</c:mi><c:mn>2</c:mn></c:msub></c:mrow></c:math> (<d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mi>T</d:mi></d:math> = Co, Rh, Ir), using ultrafast resonant x-ray diffraction. We observe a twofold increase in the ultrafast intersublattice angular momentum transfer rate between the materials, originating from modifications in the conduction electron susceptibility, as confirmed by first-principles calculations. Published by the American Physical Society 2024