Nanoscale Imaging of Strain-Controlled Altermagnetic Domains in α-MnTe

Altermagnets combine compensated magnetic order with momentum-dependent spin splitting, offering a route to spintronic functionality without the stray fields of conventional ferromagnets. Mechanical strain provides a promising means of controlling their N\'eel order, yet the microscopic pathway by which strain reorganizes an altermagnetic texture remains unresolved. Here, we integrate a piezo-driven uniaxial strain cell with scanning nitrogen-vacancy magnetometry to image the magnetic domains of bulk {\alpha}-MnTe during in situ compression at room temperature. We find that compression reorganizes the magnetic texture through domain coalescence, increasing the size of the largest connected domain while reducing the domain-wall density. Upon unloading, however, the strain-formed domain network does not retrace the loading pathway. Instead, the large connected regions fragment into a new metastable configuration, producing pronounced hysteresis in the maximum domain size and stray-field distribution. These results identify domain connectivity and topology as key carriers of strain-induced magnetic memory. Our work reveals domain coalescence and hysteretic fragmentation as the microscopic pathway of strain control in {\alpha}-MnTe and establishes a route toward strain-programmable altermagnetic textures and reconfigurable spintronic devices.