Coexistence of Giant Transverse Transport Properties and Complex Spin Configuration in Polycrystalline Kagomé Ferromagnet GdCo₂

Kagomé lattice magnets have recently garnered significant interest due to the pronounced transverse transport characteristics, particularly in thermoelectric and spintronic applications, stemming from the interplay between topology and magnetism. Here, a comprehensive investigation of the magnetic, electrical, and thermoelectric transport properties, as well as the complex spin configurations, is conducted in a polycrystalline Kagomé ferromagnet GdCo₂. Strikingly, a giant anomalous Hall conductivity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>σ</mml:mi> <mml:mrow><mml:mi>y</mml:mi> <mml:mi>x</mml:mi></mml:mrow> <mml:mi>A</mml:mi></mml:msubsup> <mml:annotation>$\sigma _{yx}^A$</mml:annotation></mml:semantics> </mml:math> ≈2125 S cm^-1 is obtained at T = 10 K, which is primarily governed by the extrinsic skew-scattering mechanism. Simultaneously, a large anomalous Nernst effect, including both the Nernst coefficient ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>S</mml:mi> <mml:mrow><mml:mi>y</mml:mi> <mml:mi>x</mml:mi></mml:mrow> <mml:mi>A</mml:mi></mml:msubsup> <mml:annotation>$S_{yx}^A$</mml:annotation></mml:semantics> </mml:math> ≈3.5 µV K^-1 at 250 K) and transverse thermoelectric conductivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>α</mml:mi> <mml:mrow><mml:mi>y</mml:mi> <mml:mi>x</mml:mi></mml:mrow> <mml:mi>A</mml:mi></mml:msubsup> <mml:annotation>$\alpha _{yx}^A$</mml:annotation></mml:semantics> </mml:math> ≈3.2 A m^-1 K^-1 at 210 K) are achieved, which surpass most of the typical Kagomé magnets. In addition, both appreciable topological Hall and Nernst effects imply the emergence of nontrivial spin structures in GdCo₂, correlating with the M-shaped MR(H) behavior. The remarkable observations of stable spontaneous Skyrmion bubbles and vortices in GdCo₂ further substantiate the above conjecture. This study highlights the coexistence of multiple intriguing physical phenomena, making the Kagomé ferromagnet GdCo₂ serve as a promising candidate for exploring transverse transport effects and the extremely rich underlying physics.