Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles

Abstract Exchange bias properties of MnFe $$_2$$ 2 O $$_4$$ 4 @ $$\gamma$$ γ –Fe $$_2$$ 2 O $$_3$$ 3 core–shell nanoparticles are investigated. The measured field and temperature dependencies of the magnetization point out a well-ordered ferrimagnetic core surrounded by a layer with spin glass-like...

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Autores principales:	F. G. Silva, J. Depeyrot, Yu. L. Raikher, V. I. Stepanov, I. S. Poperechny, R. Aquino, G. Ballon, J. Geshev, E. Dubois, R. Perzynski
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/0b4b3c17e92d4ce8b37a22ea8f81edf1
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spelling	oai:doaj.org-article:0b4b3c17e92d4ce8b37a22ea8f81edf12021-12-02T11:35:58ZExchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles10.1038/s41598-021-84843-02045-2322https://doaj.org/article/0b4b3c17e92d4ce8b37a22ea8f81edf12021-03-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-84843-0https://doaj.org/toc/2045-2322Abstract Exchange bias properties of MnFe $$_2$$ 2 O $$_4$$ 4 @ $$\gamma$$ γ –Fe $$_2$$ 2 O $$_3$$ 3 core–shell nanoparticles are investigated. The measured field and temperature dependencies of the magnetization point out a well-ordered ferrimagnetic core surrounded by a layer with spin glass-like arrangement. Quasi-static SQUID magnetization measurements are presented along with high-amplitude pulse ones and are cross-analyzed by comparison against ferromagnetic resonance experiments at 9 GHz. These measurements allow one to discern three types of magnetic anisotropies affecting the dynamics of the magnetic moment of the well-ordered ferrimagnetic NP’s core viz. the easy-axis (uniaxial) anisotropy, the unidirectional exchange-bias anisotropy and the rotatable anisotropy. The uniaxial anisotropy originates from the structural core–shell interface. The unidirectional exchange-bias anisotropy is associated with the spin-coupling at the ferrimagnetic/spin glass-like interface; it is observable only at low temperatures after a field-cooling process. The rotatable anisotropy is caused by partially-pinned spins at the core/shell interface; it manifests itself as an intrinsic field always parallel to the external applied magnetic field. The whole set of experimental results is interpreted in the framework of superparamagnetic theory, i.e., essentially taking into account the effect of thermal fluctuations on the magnetic moment of the particle core. In particular, it is found that the rotatable anisotropy of our system is of a uniaxial type.F. G. SilvaJ. DepeyrotYu. L. RaikherV. I. StepanovI. S. PoperechnyR. AquinoG. BallonJ. GeshevE. DuboisR. PerzynskiNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-10 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q F. G. Silva J. Depeyrot Yu. L. Raikher V. I. Stepanov I. S. Poperechny R. Aquino G. Ballon J. Geshev E. Dubois R. Perzynski Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
description	Abstract Exchange bias properties of MnFe $$_2$$ 2 O $$_4$$ 4 @ $$\gamma$$ γ –Fe $$_2$$ 2 O $$_3$$ 3 core–shell nanoparticles are investigated. The measured field and temperature dependencies of the magnetization point out a well-ordered ferrimagnetic core surrounded by a layer with spin glass-like arrangement. Quasi-static SQUID magnetization measurements are presented along with high-amplitude pulse ones and are cross-analyzed by comparison against ferromagnetic resonance experiments at 9 GHz. These measurements allow one to discern three types of magnetic anisotropies affecting the dynamics of the magnetic moment of the well-ordered ferrimagnetic NP’s core viz. the easy-axis (uniaxial) anisotropy, the unidirectional exchange-bias anisotropy and the rotatable anisotropy. The uniaxial anisotropy originates from the structural core–shell interface. The unidirectional exchange-bias anisotropy is associated with the spin-coupling at the ferrimagnetic/spin glass-like interface; it is observable only at low temperatures after a field-cooling process. The rotatable anisotropy is caused by partially-pinned spins at the core/shell interface; it manifests itself as an intrinsic field always parallel to the external applied magnetic field. The whole set of experimental results is interpreted in the framework of superparamagnetic theory, i.e., essentially taking into account the effect of thermal fluctuations on the magnetic moment of the particle core. In particular, it is found that the rotatable anisotropy of our system is of a uniaxial type.
format	article
author	F. G. Silva J. Depeyrot Yu. L. Raikher V. I. Stepanov I. S. Poperechny R. Aquino G. Ballon J. Geshev E. Dubois R. Perzynski
author_facet	F. G. Silva J. Depeyrot Yu. L. Raikher V. I. Stepanov I. S. Poperechny R. Aquino G. Ballon J. Geshev E. Dubois R. Perzynski
author_sort	F. G. Silva
title	Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
title_short	Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
title_full	Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
title_fullStr	Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
title_full_unstemmed	Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
title_sort	exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/0b4b3c17e92d4ce8b37a22ea8f81edf1
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_version_	1718395802566524928

Exchange-bias and magnetic anisotropy fields in core–shell ferrite nanoparticles

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