Local Investigation of the Altermagnetic Phase in Co0.25TaSe2 through Muon Spin Relaxation

Altermagnetism, a recently discovered magnetic order bridging ferromagnetism and antiferromagnetism, is highly promising for next-generation spintronics due to its spin-polarized bands without net magnetization. Intercalated transition metal dichalcogenides (ITMDs) like Co0.25TaSe2 (T_N ~ 125 K) are emerging benchmark systems for this phenomenon, exhibiting A-type antiferromagnetic order and spin-split electronic bands. However, bulk measurements leave critical microscopic details unresolved, specifically the degree of magnetic homogeneity, the volume fraction of the ordered state, and the presence of precursor spin fluctuations. We propose zero-field (ZF) and longitudinal-field (LF) muon spin relaxation (muSR) experiments on a high-purity powder sample of Co0.25TaSe2 using the HIFI instrument at ISIS. muSR is the essential local probe required to quantitatively determine the internal magnetic field distribution, distinguish between static and dynamic magnetic components, and search for potential altermagnetic fluctuations above T_N. This research will provide the necessary microscopic foundation to establish Co0.25TaSe2 as a core platform for understanding the interplay of magnetism, symmetry, and itinerant electronic states in this new class of materials. We request 2 days (6 shifts) of beam time to complete the comprehensive ZF temperature scan (20 - 200 K) and the targeted LF studies.