Pressure-tuned magnetism and band-gap modulation in layered Fe-doped CrCl₃

We report a comprehensive investigation of the structural, magnetic, vibrational, and optical properties of Fe-doped CrCl3 under varying external pressures. By integrating high-pressure experimental techniques, including Raman spectroscopy, photoluminescence (PL), magnetization, and thermal expansion measurements, with density functional theory (DFT) calculations, we uncover pressure-driven phase and magnetic transitions in this layered van der Waals material. At ambient pressure, Raman spectra exhibit all six expected Raman-active modes, which systematically blueshift with increasing pressure. A distinct change occurs in A3g mode near 9.2 GPa, suggesting an isostructural phase transition (IST), similar to that observed in pristine CrCl3 around 11 GPa. PL measurements indicate a band gap of 1.48 eV at approximately 0.6 GPa, which increases with pressure up to 9.2 GPa, followed by a slight decrease beyond this point. This further confirms the occurrence of the IST. Magnetization measurements at ambient pressure under 0.001 T magnetic field reveal two magnetic transitions: TN at 14.3 K and TC at 16 K, indicating the coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) phases. Upon applying pressure, TN and TC gradually become suppressed, and TN disappears by 2 GPa. The transition width associated with TC broadens beyond 0.5 GPa, highlighting the pressure-enhanced FM behavior. Field-dependent magnetization at ambient pressure shows complete suppression of TN above 0.4 T, with FM ordering dominating at higher fields. At 1.2 GPa, both TN and TC shift to lower temperatures. Notably, TN is suppressed above 0.2 T and only FM order remains. Gr & uuml;neisen analysis of the uniaxial thermal expansion confirms the competition between FM and AFM interactions and yields very large uniaxial pressure effects of-143%/GPa and +43%/GPa, at TN and TC, respectively. DFT calculations for pure CrCl3 are consistent with experimental data and predict a pressure-induced suppression of interlayer AFM exchange, accompanied by the stabilization of FM intralayer coupling through enhanced Cr-Cl-Cr superexchange pathways. These calculations suggest an AFM-to-FM interlayer stacking transition occurring near 1 GPa. Furthermore, increasing Fe doping appears to support the persistence of AFM character. Our findings establish Fe-doped CrCl3 as a promising platform for pressure-tunable magnetism. The ability to manipulate FM and AFM interactions through external pressure and magnetic fields opens avenues for applications in sensors, spintronic devices, and other functional two-dimensional magnetic systems.