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Physics & Astronomy International Journal

Mini Review Volume 2 Issue 5

The role of α–Fe and metal oxides nanoparticles on the structural properties of high–temperature spintronic EuO:Fe composite

Arnold S Borukhovich

Russian State Vocational Pedagogical University, Yekaterinburg, Russia

Correspondence: Arnold S Borukhovich, Russian State Vocational Pedagogical University, Mashinostroiteley Str.,11, Yekaterinburg, Russia

Received: April 20, 2018 | Published: October 11, 2018

citation: Borukhovich AS. The role of ? –Fe and metal oxides nanoparticles on the structural properties of high–temperature spintronic EuO:Fe composite. Phys Astron Int J. 2018;2(5):465-466. DOI: 10.15406/paij.2018.02.00125

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Abstrat

Based on the available experimental and theoretical data, the role of the a–Fe nanoparticles and higher metallic oxides in the structure of the EuO: Fe composite on the formation of a complex of inherent physical parameters is tracked. That along with the presence of a limited solid solution Eu1–xFexO in its structure contributes to the chemical stability of this high–temperature spin injector under normal conditions.

Introduction

It is considered that metallic iron does not dissolve in europium monoxide and does not form an independent crystalline phase with it as a solid solution (SS) Eu1–xFexO.1 However, this does not mean that such SSs are not able to originate at least partially or in limited regions of compositions in more complex multiphase composites containing europium and iron oxides. In particular, in the spintronic composite material synthesized from higher oxides of europium (Eu2O3) and iron (Fe2O3) by the high–temperature solid–phase reduction method. It has been experimentally confirmed2 that several more independent crystalline phases co–exist in such composite in addition to the above–mentioned SS: from nanosized super paramagnetic particles of metallic iron to oxides of both metals in different oxidation states. However, it is the presence of this SS that determines the outstanding physical characteristics of this composite – its high specific magnetization (40–60emu/g at the room temperatures, Tr) and the Curie temperature, T c =480K MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGubWcpaWaaSbaaKqaGeaajugWa8qacaWG JbaajeaipaqabaqcLbsapeGaeyypa0JaaGinaiaaiIdacaaIWaGaam 4saaaa@4387@ . Under the conditions of its inherent semiconductor conductivity at the range of compositions 0.15<x<0.25 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaaIWaGaaiOlaiaaigdacaaI1aGaeyipaWJa amiEaiabgYda8iaaicdacaGGUaGaaGOmaiaaiwdaaaa@440D@ , this composite material is promising in the creation of semiconductor spintronic devices capable of stable operation at the room temperature. At the same time an increased degree is achieved of spin current transfer, P60% MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGqbGaeyisISRaaGOnaiaaicdacaGGLaaa aa@3FE4@ .3,4 To the latter in a great extent contributes the chemical stability of this composite, located both in bulk and in thin–film states in normal environmental conditions. Such stability is largely ensured by the adherence to the composite of the aforementioned nanoparticles.

Experimental

In support of the above, we present the results of the experimental studies of resonance (nuclear magnetic resonance, NGR) and magnetic parameters of this composite. Thus, the spectra of nuclear magnetic resonance (or the Mössbauer effect) of a bulk sample of the EuO:Fe composite for the 57Fe isotope, taken at room temperature are presented in Figure 1. It’s characterizes a typical ferromagnet and contain at least two sixes of Zeeman lines which are related to α–Fe nanoparticles and Eu–Fe–O clusters, respectively.

Figure 1 NGR spectra of 57Fe powder of the EuO: Fe composite at room temperature.

In the same conditions the Mössbauer spectra of 57Fe of the composite films represent a singlet with an isomeric shift of δ=+0.20mm/s and with a very weak splitting, typical for the display of super paramagnetism of α–Fe nanoparticles. This data exeplifies that the high–temperature magnetism of the composite is caused by the presence of the ferromagnetic ordering of Eu–Fe–O clusters and super paramagnetic α–Fe nanoparticles. This is fully confirmed by magnetic studies of the composite.

The cation state of the europium atoms in the composite illustrates the NGR spectrum of 151Eu. It is an overlap of two lines characterized by isomeric shifts of δ=12.6mm/s MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacqaH0oazcqGH9aqpcqGHsislcaaIXaGaaGOm aiaac6cacaaI2aGaamyBaiaad2gacaGGVaGaam4Caaaa@454B@  and δ=+0.02mm/s MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacqaH0oazcqGH9aqpcqGHRaWkcaaIWaGaaiOl aiaaicdacaaIYaGaamyBaiaad2gacaGGVaGaam4Caaaa@4539@ . The first line corresponds to the paramagnetic ion of the Eu2+ matrix. The second line is responsible for the manifestation of the valence state of Eu3+.3

The studies of the magnetization dependence upon cooling of the composite films at low temperatures in an external magnetic field (the FC condition) and without a field (the ZFC condition) revealed another feature.4 Namely, the presence of an inflection of this dependence in the temperature region of T=25÷30K MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGubGaeyypa0JaaGOmaiaaiwdacqGH3daU caaIZaGaaGimaiaadUeaaaa@4317@ (Figure 2) in the latter case. This so–called “blocking temperature” (Tbl) – is the transition from the antiferromagnetically ordered state (at T<Tbl) to super paramagnetism (at T T bl MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGubGaeyizImQaamivaSWdamaaBaaajeai baqcLbmapeGaamOyaiaadYgaaKqaG8aabeaaaaa@4256@ ) of α MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacqaHXoqyaaa@3CDA@ –iron nanoparticles in the composite.

Physically this means that the magnetic moments of such nanoparticles at T T bl MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGubGaeyizImQaamivaSWdamaaBaaajeai baqcLbmapeGaamOyaiaadYgaaKqaG8aabeaaaaa@4256@ are antiferromagnetically in relation to ferromagnetically ordered state of the matrix Eu2+ ions. At T> T bl MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbdfwBIj xAHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1B TfMBaebbnrfifHhDYfgasaacPi=BMipgYlb91rFfpec8Eeeu0xXdbb a9frFj0=OqFfea0dXdd9vqaq=JfrVkFHe9pgea0dXdar=Jb9hs0dXd bPYxe9vr0=vr0=vqpWqaaeaabiGaciaacaqabeaadaabauaaaOqaaK qzGeaeaaaaaaaaa8qacaWGubGaeyOpa4JaamivaSWdamaaBaaajeai baqcLbmapeGaamOyaiaadYgaaKqaG8aabeaaaaa@41A9@ , the situation changes–superparamagnetism of α–Fe nanoparticles promotes the growth of the magnetic moment of the Eu–Fe–O clusters.

Figure 2 The magnetization of the (EuO)0.75Fe0.25 composite film under conditions of ZFC and FC.

In conclusion, we note that this combination of phase components, which form the outstanding properties of this composite as a high–temperature spintronic material, may be reproduced only when it is synthesized from higher oxides. Attempts to synthesize the aforementioned single–phase SS from the metals corresponding to the properties of the composite have so far been unsuccessful.5

Acknowledgements

None.

Conflict of interest

The author declares there is no conflict of interest.

References

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©2018 Borukhovich. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and build upon your work non-commercially.