Local Ligand-Framework Evolution Prior to Long-Range Antiferromagnetic Ordering in NiPS3.

Abstract

Two-dimensional van der Waals antiferromagnets have emerged as a promising platform for low-dimensional spintronics. NiPS3 is a representative system because of its negligible stray fields and ultrafast spin dynamics. However, the relationship between local structural evolution and the establishment of long-range antiferromagnetic order remains incompletely understood. Here, we investigate the temperature-dependent magnetostructural evolution of NiPS3 using anisotropic magnetization measurements, neutron powder diffraction, variable-temperature powder X-ray diffraction Rietveld refinement, Raman spectroscopy, and maximum entropy method electron density reconstruction. Anisotropic magnetization and its temperature derivatives reveal a broad, orientation-dependent magnetic response over approximately 157-164 K. Neutron diffraction detects additional intensity near the magnetic (010) reflection at 150 K, whereas no comparable magnetic Bragg feature is resolved at 160 or 166 K under the present measurement conditions, indicating that the higher-temperature magnetic response is not accompanied by resolvable long-range magnetic Bragg scattering. Structural refinements, Raman spectroscopy, and electron density analyses further identify complementary local structural, vibrational, and electronic responses within the 162-164 K portion of this broad magnetic response interval. Together, these results place the local structural response within the upper part of the magnetic-response interval and before the development of resolvable long-range antiferromagnetic order at lower temperatures. These findings provide an experimental framework for examining magnetostructural evolution and ligand-mediated tuning of magnetism in layered antiferromagnets.

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