Spin-phonon coupling (SPC) is vital in two-dimensional magnetic materials (2DMMs), correlating charge, spin, and lattice vibrations, which is significant for fundamental physics and spintronics. ${\mathrm{CrTe}}_2$, a 2DMM with high Curie temperature, forms self-intercalated ${\mathrm{Cr}}_{1+\mathrm{x}}{\mathrm{Te}}_2$ by interlayer Cr intercalation to easily tune its ground-state properties, promising as a next-generation spintronics device. However, SPC and the microscopic magnetic mechanism (MMM) of ${\mathrm{Cr}}_{1+\mathrm{x}}{\mathrm{Te}}_2$ are still an open issue. Interestingly, studies have found that its magnetic transition temperature is sensitive to the amount of Cr intercalation, while in the critical case of $x_{\mathrm{C}}\sim 0.5$, the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions enhances magnetic fluctuations, providing a potential platform for studying SPC and MMM. Here, we focus on ${\mathrm{Cr}}_{1.45}{\mathrm{Te}}_2$ crystals near critical doping, systematically investigating their magnetic and thermal properties to clarify related issues. ${\mathrm{Cr}}_{1.45}{\mathrm{Te}}_2$, with a NiAs-type structure ($P\overline{3}m1$), shows pronounced magnetic anisotropy with an out-of-plane FM transition at 232 K and an in-plane AFM transition at 228 K. Lattice dynamics reveal asymmetric $A_{1\mathrm{g}}$ ($\sim 15.1\mathrm{meV}$) and symmetric $E_{\mathrm{g}}$ ($\sim 17.3\mathrm{meV}$) phonon anomalies, attributed to strong SPC, suggesting that ${\mathrm{Cr}}_{1.45}{\mathrm{Te}}_2$ could be a promising candidate for SPC. Furthermore, the strong overlap of Cr $3d_z^2\text{–}\mathrm{Cr}3d_z^2$ induces interlayer FM direct exchange, and in-plane AFM superexchange via near ${180}^{\circ }\mathrm{Cr}\text{–}\mathrm{Te}\text{–}\mathrm{Cr}$ bonding transforms into the plausible Dzyaloshinskii-Moriya interaction due to the robust spin-orbit coupling of Te and relativistic corrections, forming a noncollinear AFM order. Thus, SPC and the competition of magnetic interactions causes intriguing thermomagnetic irreversibilities such as cluster glass, and magnetic thermal hysteresis formed by domain-wall pinning. Notably, ${\mathrm{Cr}}_{1.45}{\mathrm{Te}}_2$ also exhibits a canted noncollinear AFM ground-state and rich excited-state evolution with temperature and applied fields, which will promote the future development of spintronics. This study provides insights to understand SPC and MMM for CrTe-based materials.

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• Domain walls
• Exchange interaction
• Magnetic anisotropy
• Magnetic phase transitions
• Spin-phonon coupling
• Layered crystals
• Electron spin resonance
• Magnetic force microscopy
• Raman spectroscopy