Polymorphic spin ordering in a single-crystalline cobalt-doped Fe3GaTe2

Woohyun Cho; Jaehun Cha; Yoon-Gu Kang; Dong Hyun David Lee; Jaehwan Oh; Dohyun Kim; Sangsu Yer; Jaein Lee; Heemyoung Hong; Yongsoo Yang; Yeong Kwan Kim; Myung Joon Han; Heejun Yang

arXiv · 2505.05198

Polymorphic spin ordering in a single-crystalline cobalt-doped Fe3GaTe2

Woohyun Cho·Jaehun Cha·Yoon-Gu Kang·Dong Hyun David Lee·Jaehwan Oh·Dohyun Kim·Sangsu Yer·Jaein Lee·Heemyoung Hong·Yongsoo Yang·Yeong Kwan Kim·Myung Joon Han·Heejun Yang

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Abstract

A single crystalline system typically stabilizes a unique state for spin ordering below a critical temperature. Certain materials exhibit multiple magnetic states, driven by structural phase transitions under varying thermodynamic conditions. Recently, van der Waals magnets have demonstrated subtle interlayer exchange interactions, offering a promising approach to electrically control spin states without structural transformation. Here, we report the emergence of three distinct magnetic states, ferromagnetic ordering and both collinear and non-collinear antiferromagnetic orderings, in a layered single crystalline magnet, cobalt-doped Fe3GaTe2 ((Co, Fe)3GaTe2). These three magnetic phases occur without structural phase transitions, a phenomenon we designate as polymorphic spin ordering in the material. The introduction of 16% Co-doping in Fe3GaTe2 modulates the interlayer magnetic interaction, enabling multiple spin orderings within the same lattice system with three critical temperatures: a Curie temperature for a ferromagnetic state (Tc=210 K) and two Neel temperatures for the collinear (TN1=110 K) and non-collinear (TN2=30 K) antiferromagnetic states. Our findings are supported by magnetic force microscopy, first-principles calculations, and circular dichroism angular photoemission spectroscopy, which reveals varying spin ordering and changes in the topological band structure and Berry curvature at different temperatures within the single-crystalline (Co, Fe)3GaTe2.

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Woohyun Cho, Jaehun Cha, Yoon-Gu Kang, Dong Hyun David Lee, Jaehwan Oh, Dohyun Kim, Sangsu Yer, Jaein Lee, Heemyoung Hong, Yongsoo Yang, Yeong Kwan Kim, Myung Joon Han, Heejun Yang. 2025-05-08. Polymorphic spin ordering in a single-crystalline cobalt-doped Fe3GaTe2. https://arxiv.org/abs/2505.05198

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