Magnetic frustration enforced electronic reconstruction in Ni-intercalated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>NbSe</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> : Suppression of electronic orders

We investigate the single crystals of ${\mathrm{Ni}}_{0.19}{\mathrm{NbSe}}_{2}$, revealing that Ni intercalation profoundly alters the physical properties of ${\mathrm{NbSe}}_{2}$. Magnetic measurements clearly show that the system is magnetically frustrated with antiferromagnetic ordering below 23.5 K, with an irreversibility temperature near 10 K, and a magnetic hysteresis with a small net magnetic moment. Overall, the system can be described as an inhomogeneous antiferromagnetic phase with magnetic disorder and magnetic frustration. We found two Curie-Weiss temperatures of --80 K for the field in the $ab$ plane and --137 K for the field out of plane, which are a consequence of anisotropic interactions in spin space and favor an orientation of the spin along the $c$ axis. Temperature-dependent resistivity shows a complete suppression of both charge density waves and superconducting order down to 300 mK. Angle-resolved photoemission spectroscopy at 84 K reveals a $\overline{\mathrm{\ensuremath{\Gamma}}}$-centered electron pocket in ${\mathrm{Ni}}_{0.19}{\mathrm{NbSe}}_{2}$, which is absent in pristine ${\mathrm{NbSe}}_{2}$. The electronic structure results show a shift of the van Hove singularity (VHS), which is the main cause of the suppression of the electronic orders. These results align with recent theoretical predictions that Ni intercalation with cationic disorder favors frustrated antiferromagnetic stripe states, shifts the VHS and reconstructs the Fermi surface in ${\mathrm{NbSe}}_{2}$. Our findings position ${\mathrm{Ni}}_{0.19}{\mathrm{NbSe}}_{2}$ within a magnetically frustrated, nonsuperconducting regime, highlighting how partial intercalation and disorder drive complex magnetic order and the Fermi surface reconstruction in low-dimensional quantum materials.