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Open AccessArticle

Glassy Magnetic Behavior and Correlation Length in Nanogranular Fe-Oxide and Au/Fe-Oxide Samples

1
Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, I-44122 Ferrara, Italy
2
Dipartimento SIMAU, Università Politecnica delle Marche, I-60131 Ancona, Italy
3
Dipartimento di Ingegneria Industriale, Università di Padova, I-35131 Padova, Italy
*
Author to whom correspondence should be addressed.
Materials 2019, 12(23), 3958; https://doi.org/10.3390/ma12233958
Received: 3 November 2019 / Revised: 18 November 2019 / Accepted: 26 November 2019 / Published: 29 November 2019
(This article belongs to the Special Issue Magnetic Nanomaterials)
In nanoscale magnetic systems, the possible coexistence of structural disorder and competing magnetic interactions may determine the appearance of a glassy magnetic behavior, implying the onset of a low-temperature disordered collective state of frozen magnetic moments. This phenomenology is the object of an intense research activity, stimulated by a fundamental scientific interest and by the need to clarify how disordered magnetism effects may affect the performance of magnetic devices (e.g., sensors and data storage media). We report the results of a magnetic study that aims to broaden the basic knowledge of glassy magnetic systems and concerns the comparison between two samples, prepared by a polyol method. The first can be described as a nanogranular spinel Fe-oxide phase composed of ultrafine nanocrystallites (size of the order of 1 nm); in the second, the Fe-oxide phase incorporated non-magnetic Au nanoparticles (10–20 nm in size). In both samples, the Fe-oxide phase exhibits a glassy magnetic behavior and the nanocrystallite moments undergo a very similar freezing process. However, in the frozen regime, the Au/Fe-oxide composite sample is magnetically softer. This effect is explained by considering that the Au nanoparticles constitute physical constraints that limit the length of magnetic correlation between the frozen Fe-oxide moments. View Full-Text
Keywords: disordered magnetism; super-spin glass; glassy correlation length; magnetic freezing; nanogranular Au/Fe-oxide; Fe-oxide nanocrystallites disordered magnetism; super-spin glass; glassy correlation length; magnetic freezing; nanogranular Au/Fe-oxide; Fe-oxide nanocrystallites
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MDPI and ACS Style

Del Bianco, L.; Spizzo, F.; Barucca, G.; Marangoni, G.; Sgarbossa, P. Glassy Magnetic Behavior and Correlation Length in Nanogranular Fe-Oxide and Au/Fe-Oxide Samples. Materials 2019, 12, 3958.

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