Hidden magnetic complexity in the simple van der Waals ferromagnet Ce 2 Te 5

Ce 2 Te 5 is a layered f -electron van der Waals magnet in which reduced dimensionality and inequivalent Ce sites give rise to competing magnetic interactions. We investigate its magnetic ground state using muon spin relaxation ( μ SR ), neutron powder diffraction (NPD), and inelastic neutron scattering (INS). Zero-field μ SR reveals an onset of static magnetism below T C = 5.0 ( 1 ) K , followed by an additional anomaly in the internal field at T 2 = 2.3 ( 2 ) K , consistent with features observed in bulk thermodynamic and transport measurements. In contrast, NPD data collected between 0.05 – 8 K reveal a single long-range ordered magnetic phase below T C , with the magnetic Bragg intensities vanishing at T C with no evidence for additional structural or magnetic phase transitions down to base temperature. The ordered state is characterized by a commensurate propagation vector k = ( 0 , 0 , 0 ) and ferromagnetic alignment of Ce moments along the crystallographic b axis. Remarkably, only one of the two crystallographically distinct Ce sites carries an ordered moment of ≈ 0.85 ( 3 ) μ B per Ce at 0.05 K. INS measurements establish the crystal-electric-field (CEF) energy scale of Ce 3 + , revealing low-lying excitations at 7.94 and 21.46 meV and a Kramers-doublet ground state with strong single-ion anisotropy. These results demonstrate that Ce 2 Te 5 undergoes a single symmetry-breaking magnetic transition, while additional low-temperature anomalies reflect subtle modifications of the ordered state driven by competing interactions and CEF effects.