Spin Transport Across Interfaces With the Non-Collinear Antiferromagnet Mn₃Sn.

Abstract

Non-collinear antiferromagnets such as <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> are promising materials for ultrafast spintronic applications due to their peculiar electronic structure and efficient spin-dependent transport phenomena. Here, we investigate magnetic ordering and ultrafast spin transport in c-axis oriented <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> thin films and <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> -based heterostructures with Pt and <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Ni</mi> <mn>80</mn></msub> <msub><mi>Fe</mi> <mn>20</mn></msub> </mrow> </math> . Temperature-dependent magneto-optical Kerr effect measurements confirm thermally activated switching of the <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> cluster octupole moment near the Néel temperature, while preserving predominantly in-plane magnetic order. In <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mrow><mi>Sn</mi> <mspace></mspace> <mo>|</mo> <mspace></mspace> <mi>Pt</mi></mrow> </mrow> </math> heterostructures, however, pronounced room-temperature ferromagnetic signatures are observed, including enhanced Kerr rotation and out-of-plane magnetization. Systematic magnetometry studies reveal the formation of an intermixed <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>2</mn></msub> <mi>PtSn</mi></mrow> </math> interfacial phase upon annealing. Ultrafast transport measurements using a sample with optimized interfaces show that optical excitation of <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> generates predominantly anomalous Nernst currents, with no detectable evidence of efficient spin-current injection into Pt. In contrast, <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Mn</mi> <mn>3</mn></msub> <mi>Sn</mi></mrow> </math> exhibits a significant inverse spin Hall conversion when driven by spin currents injected from <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow><msub><mi>Ni</mi> <mn>80</mn></msub> <msub><mi>Fe</mi> <mn>20</mn></msub> </mrow> </math> , reaching approximately <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>10</mn> <mspace></mspace> <mo>%</mo></mrow> </math> of the efficiency of Pt-based reference structures. The conversion efficiency is found to be independent of the relative orientation between ferromagnetic magnetization and antiferromagnetic octupole moment. Our results emphasize the importance of interface engineering for spintronic devices.