High-temperature superspin glass and low-temperature glassy exchange bias in passivated FeCo nanoparticles

Date

2025-05-15

Authors

López Martín, Raúl
Lepesant, Mathieu
Lacroix, Lise-Marie
Toro, José A. de

Director

Publisher

Elsevier
Acceso abierto / Sarbide irekia
Artículo / Artikulua
Versión publicada / Argitaratu den bertsioa

Project identifier

  • AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2021-122613OB-I00/ES/ recolecta
  • AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/CNS2022-135787/
  • AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2022-142267NB-I00/ES/ recolecta
Impacto
OpenAlexGoogle Scholar
No disponible en Scopus

Abstract

Conventional powders, dense systems of magnetic nanoparticles, often combine intra- and inter-particle magnetically glassy properties, which may complicate their interpretation. To shed light on this matter, we have studied 9 nm FeCo particles synthesized by thermal co-decomposition of metal amides after a passivation layer around 2 nm thick has formed in ambient conditions. The saturation magnetization, 117 emu/g, is consistent with the above metallic core/ferrite shell picture. The high magnetic moment and concentration of the particles yield, via strong interparticle interactions, a remarkable room temperature superspin glass-like phase (with freezing temperature above 350 K) for such small particles, as confirmed by the de Almeida-Thouless analysis. Additionally, we detect a spin glass-like freezing at the atomic scale (within the particles). Its corresponding feature, a small hump under small fields in the temperature dependence of the magnetization, closely agrees with the onset of the exchange bias effect (∼ 60 K) measured, unlike it is customary, with repeated field-coolings. The spin-disordered nature of the core/shell interface is further proved by a strong training effect of the exchange bias field, among others. This magnetic behavior offers an indirect proof of structural interface disorder even in fully passivated metallic particles.

Description

Keywords

Core-shell, Disordered materials, Magnetic interface, Nanoparticles, Spin-glass

Department

Ciencias / Zientziak / Institute for Advanced Materials and Mathematics - INAMAT2

Faculty/School

Degree

Doctorate program

item.page.cita

López-Martín, R., Lepesant, M., Lacroix, L. M., Toro, J. A. de, López-Ortega, A. (2025). High-temperature superspin glass and low-temperature glassy exchange bias in passivated FeCo nanoparticles. Surfaces and Interfaces, 65, 1-7. https://doi.org/10.1016/j.surfin.2025.106514.

item.page.rights

© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

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