Disorder driven maximum in the magnetoresistance of spin polaron systems
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arXiv
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| Autori principali: | , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866914220095832064 |
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| author | Mondal, Tanmoy Majumdar, Pinaki |
| author_facet | Mondal, Tanmoy Majumdar, Pinaki |
| contents | Ferromagnetic polarons are self trapped states of an electron in a locally spin polarised environment. They occur close to the magnetic $T_c$ 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 $\sim 20-30 \%$ at $T_c$, at fields that, in energy units, are $\sim 0.01 k_BT_c$. We find that structural disorder, in the form of pinning centers, promotes polaron formation, hugely increases the resistivity peak at $T_c$, and can enhance the magnetoresistance to $\sim 80\%$. 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_21388 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Disorder driven maximum in the magnetoresistance of spin polaron systems Mondal, Tanmoy Majumdar, Pinaki Strongly Correlated Electrons Ferromagnetic polarons are self trapped states of an electron in a locally spin polarised environment. They occur close to the magnetic $T_c$ 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 $\sim 20-30 \%$ at $T_c$, at fields that, in energy units, are $\sim 0.01 k_BT_c$. We find that structural disorder, in the form of pinning centers, promotes polaron formation, hugely increases the resistivity peak at $T_c$, and can enhance the magnetoresistance to $\sim 80\%$. 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. |
| title | Disorder driven maximum in the magnetoresistance of spin polaron systems |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2512.21388 |