Physical Justification for Negative Remanent Magnetization in Homogeneous Nanoparticles

Gu, Shuqing; He, Weidong; Zhang, Ming; Zhuang, Taisen; Jin, Yi; ElBidweihy, Hatem; Mao, Yiwu; Dickerson, James H.; Wagner, Michael J.; Torre, E. Della; Bennett, L. H.

doi:10.1038/srep06267

Cited by 24 publications

(17 citation statements)

References 53 publications

(70 reference statements)

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“…The negative coercivity as well as negative remanence magnetisation can be explained by site-specific surface anisotropy, noncollinear spin structure or antiferromagnetic coupling of particle core and shell. 20,49,61,64,65 The saturation magnetisation of nanoparticles oxidised in nitric acid decreases much faster (Fig. 3).…”

Section: Resultsmentioning

confidence: 95%

Oxidation of magnetite nanoparticles: impact on surface and crystal properties

et al. 2017

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Iron oxide nanoparticles are of great scientific interest due to their huge versatility of applications. The oxidation process of magnetite to maghemite is difficult to monitor as both iron oxide polymorphs possess connatural chemical properties. Especially the surface composition and reactivity of these nanosystems, which are most relevant for interactions with their environment, are not completely understood. Here, the oxidation of magnetite is investigated under mild and harsh conditions in order to understand the oxidation behaviour and the chemical stability of transition forms. Therefore, the oxidation process, is investigated with Raman, Mössbauer and X-ray photoelectron spectroscopy as well as X-ray diffraction and magnetometry. The multi-analytical approach allows new insights into surface composition and rearrangement according to respective different depth profiles. For both conditions investigated, the ferrous iron components are oxidised prior to structural changes in the Fe-O vibrations and crystal structure. The process starts from the outer layers and is acid catalysed. Oxidation leads to a decrease of magnetisation which still remains higher than 54 emu g −1. The charge and surface reactivity can be affected by the different oxidation methods and the irreversible adsorption of acid molecules. Biocompatibility and catalytic properties of iron oxide nanoparticles open doors to future applications.

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Section: Resultsmentioning

confidence: 95%

Oxidation of magnetite nanoparticles: impact on surface and crystal properties

et al. 2017

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“…This NRM has been observed only when the measuring field is less the coercive field (H c ) since for applied H > H c only positive values of M are observed in ZFC. This observed NRM is attributed to the coexistence of magnetically inhomogeneous regions consisting of spin clusters of a lower oxidation state and the ferromagnetic order in LSMO thin films 35,39,[41][42][43] . The growth pressure dependence of NRM is plotted in Fig.…”

Section: Magnetic Properties Of Lsmo Thin Filmsmentioning

confidence: 92%

Effects of Oxygen Modification on the Structural and Magnetic Properties of Highly Epitaxial La0.7Sr0.3MnO3 (LSMO) thin films

Kumari

Mottaghi

Huang

et al. 2020

Sci Rep

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a strong semi-metallic ferromagnet having robust spin polarization and magnetic transition temperature (T c) well above 300 K, has attracted significant attention as a possible candidate for a wide range of memory, spintronic, and multifunctional devices. Since varying the oxygen partial pressure during growth is likely to change the structural and other physical functionalities of La 0.7 Sr 0.3 MnO 3 (LSMO) films, here we report detailed investigations on structure, along with magnetic behavior of LSMO films with same thickness (~30 nm) but synthesized at various oxygen partial pressures: 10, 30, 50, 100, 150, 200 and 250 mTorr. The observation of only (00 l) reflections without any secondary peaks in the XRD patterns confirms the high-quality synthesis of the above-mentioned films. Surface morphology of the films reveals that these films are very smooth with low roughness, the thin films synthesized at 150 mTorr having the lowest average roughness. The increasing of magnetic T c and sharpness of the magnetic phase transitions with increasing oxygen growth pressure suggests that by decreasing the oxygen growth pressure leads to oxygen deficiencies in grown films which induce oxygen inhomogeneity. Thin films grown at 150 mTorr exhibits the highest magnetization with T C = 340 K as these thin films possess the lowest roughness and might exhibit lowest oxygen vacancies and defects. Interpretation and significance of these results in the 30 nm LSMO thin films prepared at different oxygen growth pressures are also presented, along with the existence and growth pressure dependence of negative remanent magnetization (NRM) of the above-mentioned thin films. The miniaturization of devices to increase speed and reduce the cost of materials is an ongoing need for many current and potential magnetic technologies such as spintronics, highly dense non-volatile memory, spin-caloritronics, and different multifunctional micro and nanoscale devices 1-5. Among important materials for device applications are room temperature ferromagnetic oxides such as the manganites, La 1−x Sr x MnO 3 , since their properties can be tuned using a number of degrees of freedom including charge, spin, orbital, and magnetic ordering phenomena 6,7. They are also excellent candidates for novel engineered nanostructures as they exhibit colossal magnetoresistance (CMR) effect which has been used for different multifunctional applications 8-10. La 1− x Sr x MnO 3 also shows CMR phenomena under smaller external magnetic fields compared to the other manganites and strongly correlated materials 11,12. Among the La 1−x Sr x MnO 3 manganites, the optimized stoichiometry La 0.7 Sr 0.3 MnO 3 (LSMO) is one of the most prominent members with outstanding magnetic and magneto-transport properties. Compared to other typical magnetic oxides, LSMO exhibits semi-metallic behavior, outstanding ferromagnetism, high Fermi-level spin polarization, with a bulk magnetic ordering temperature, T C (= 370 K) well above room temperature 13,14. Also, the spin polarization of LSMO ...

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“…The magnetization achieves the reversible magnetization M rev (anti-hysteresis curves) in an infinite time (1), see Fig. 11 and [10]. Some obstacle stops domains wall motion sooner and they do not move further regarding to the measuring accuracy.…”

Section: Discussionmentioning

confidence: 96%

Difficulties Caused by Magnetic After-effect during Identification of the Preisach Hysteresis Model Weighting Function

Novák

2019

Acta Phys. Pol. A

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The time dependence of the magnetic hysteresis caused by thermal activation over an energy barrier is called after-effect, magnetic viscosity, or magnetic relaxation. Magnetic after-effect influences the hysteresis loop shape depending on an excitation filed rate of change, the sample geometry, and the state. The magnetizing loop changes, especially at rounding of peaks at steep part of the loop, severely influences process of the Preisach model weighting function identification from experimental data. This article deals with the after-effect measuring with the aim of determining limiting excitation speed.

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Physical Justification for Negative Remanent Magnetization in Homogeneous Nanoparticles

Cited by 24 publications

References 53 publications

Oxidation of magnetite nanoparticles: impact on surface and crystal properties

Oxidation of magnetite nanoparticles: impact on surface and crystal properties

Effects of Oxygen Modification on the Structural and Magnetic Properties of Highly Epitaxial La0.7Sr0.3MnO3 (LSMO) thin films

Difficulties Caused by Magnetic After-effect during Identification of the Preisach Hysteresis Model Weighting Function

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