Evolution at the nanoscale of magnetic clustering of the Griffiths-like phase in Tb4.925La0.075Si2Ge2
Griffiths-like phases (GP) are connected to disordered magnetic nanostructures. Here, we focus on the Giant Magnetocaloric compound Tb5−LaSi2Ge2 with x = 0.075 where a re-entrant cluster-glass state (CGS) emerges at a characteristic freezing temperature T ∼ 140 K within the GP (110–180 K), i.e. abov...
| Autores: | , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/403596 |
| Acceso en línea: | http://hdl.handle.net/10261/403596 |
| Access Level: | acceso abierto |
| Palabra clave: | Rare earth alloys Griffiths-like phase Cluster-spin glass Ageing Small angle neutron scattering |
| Sumario: | Griffiths-like phases (GP) are connected to disordered magnetic nanostructures. Here, we focus on the Giant Magnetocaloric compound Tb5−LaSi2Ge2 with x = 0.075 where a re-entrant cluster-glass state (CGS) emerges at a characteristic freezing temperature T ∼ 140 K within the GP (110–180 K), i.e. above the Curie temperature (T). This unconventional magnetic state has been studied via temperature-dependent DC magnetization (5–300 K), time-dependent macroscopic AC susceptibility (80–200 K), including ageing and memory experiments, and magnetic small-angle neutron scattering (SANS), above T(110–250 K). This approach allows to reveal the microscopic structure of the GP at the nanoscale in this system. AC susceptibility and DC magnetization confirm the presence of interacting short-range (< 2 nm) ferromagnetic (FM) clusters in the GP. The Langevin-like field dependence of the isothermal magnetization provides a quantitative assessment of the temperature dependence of the cluster size. Memory effects and ageing phenomena within GP are indicative of magnetically-frustrated states. Our results reveal that the dynamics is affected by the progressive coupling among CGS and GP towards the FM state. SANS correlation lengths between 1-5 nm above T are determined from the calculated magnetic correlation function C(r), which is computed from the magnetic SANS intensity. A phenomenological model based on the formation of FM clusters with intercluster (FM) interactions within a PM matrix is proposed to explain the unusual re-entrant glassy behaviour in the PM state. These findings serve as another experimental reference for the global understanding of disordered magnetic compounds. |
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