Phase separation and magnetic polarons in colossal magnetoresistance systems

A ubiquitous characteristic of colossal magnetoresistance (CMR) materials with competing interactions is a rich phase diagram, in which many phases exhibit intrinsic (i.e. electronic, and nonchemical) phase separation, often leading to transitions that are percolative in nature. Indeed, nanoscale electronic phase separation is thought to play a crucial role in the emergence of CMR, as well as in the suppression of critical dynamics in quantum phase transitions. Here we propose muSR measurements on two systems exhibiting a CMR effect: HgCr2Se4 and Eu5In2Sb6. Both materials show magnetic transitions coupled to electronic properties that vary over an extended temperature regime, which are likely to reflect phase separation, slow magnetic dynamics and the possibility of emergent magnetic polaron states.