2025/12/24 by Tanmoy Mondal, Pinaki Majumdar, Mondal, Tanmoy +1
Materials Science · Physics and Astronomy · #Electronic and Structural Properties of Oxides #FOS: Physical sciences #Quantum and electron transport phenomena #Strongly Correlated Electrons (cond-mat.str-el) #Topological Materials and Phenomena
paper · doi:10.48550/arxiv.2512.21388
openalex publication_date 2025/12/24 · openalex created_date 2025/12/30 · openalex updated_date 2026/07/28
Ferromagnetic polarons are self trapped states of an electron in a locally spin polarised environment. They occur close to the magnetic Tc in low carrier density local moment magnets when the electron-spin coupling is comparable to the hopping scale. In non disordered systems the primary signatures are a modest non-monotonicity in the temperature dependent resistivity ρ(T), and a magnetoresistance that can be ∼ 20-30 % at Tc, at fields that, in energy units, are ∼ 0.01 kBTc. We find that structural disorder, in the form of pinning centers, promotes polaron formation, hugely increases the resistivity peak at Tc, and can enhance the magnetoresistance to ∼ 80%. The change in magnetoresistance with disorder is, however, non-monotonic. Too much disorder just creates an Anderson insulator - with the resistivity unresponsive to the magnetisation. This paper establishes the optimum disorder for maximising the magnetoresistance, suggests the physical process behind the unusual disorder dependence, and provides a magnetoresistance map - in terms of coupling and disorder - that locates some of the existing magnetic semiconductors within this framework.