Magnetoresistance in magnetite: Switching of the magnetic easy axis

Król, G.; Tabiś, Wojciech; Przewoźnik, J.; Kołodziej, Tomasz; Ka̧kol, Z.; Kozłowski, A.; Tarnawski, Z.

doi:10.1016/j.jallcom.2008.09.171

Cited by 7 publications

(9 citation statements)

References 9 publications

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“…We have made several resistivity measurements [32] with the stoichiometric single crystalline magnetite sample with two sets of contacts attached to it (one set along [0 1 0], the other along [1 0 0]). This set-up was used to simultaneously measure resistance in two directions, first with magnetic field B along c axis and then in other h1 0 0i direction, perpendicular to c.…”

Section: Electrical Transport Response To the Axis Switchingmentioning

confidence: 99%

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Ka̧kol

Kozłowski

Kołodziej

et al. 2015

Philosophical Magazine

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Magnetite is the oldest magnet and the first material where the concept of a strong correlations driven metal-insulator transition was suggested and found at T V = 124 K in the so-called Verwey phase transformation. Recently, the structure below T V was solved revealing subtle electronic structure in the form of trimeron lattice that, according to yet another recent communication, may be switched within femtosecond range. In this review article, we argue that the same change of trimeron lattice can be achieved by a magnetic field, in the phenomenon called the easy axis switching. The results of many of our experiments show that although this process is best viewed by magnetization studies, it is also reflected in magnetostriction, causes some changes in electronic transport and can be observed microscopically by NMR that proved electronic order alteration. All those facts suggest that the axis switching process observed and studied by us is intimately linked with the fast change of electronic trimeron order mentioned above.Probably none of the naturally existing minerals was utilized by mankind and nature more in its pristine form than magnetite. Navigation in the world, both by artificial and natural compasses, storage media and, finally, the tool in the emerging field of spin electronics are a few examples only. But despite its role in civilization, magnetite displays yet another fascinating face: the Verwey transition (VT). In this first-order phase transformation, the resistivity drops two orders of magnitude when heated above T V = 124 K. Surprisingly, all groups of magnetite "application" and the Verwey transition are interwoven: cooling down magnetite below T V results in a drastic drop of electric conductivity, affecting its spintronic application and the thermal cycling across the transition greatly diminishes coercive force, i.e. magnetic memory (see e.g. [1]). This transition is the subject of our extensive studied described below.Not only resistivity jumps at T V ; the spectacular anomalies are observed practically in all physical characteristics. In particular, there is a huge peak in heat capacity, proving first-order character of the transition and the structure symmetry changes. The hightemperature magnetite structure was found of inverse spinel type, with Fd 3m symmetry and with Fe residing in tetrahedral and octahedral positions. When cooled below T V ,

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Section: Electrical Transport Response To the Axis Switchingmentioning

confidence: 99%

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Ka̧kol

Kozłowski

Kołodziej

et al. 2015

Philosophical Magazine

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“…The intensity of this reflection vs increasing magnetic field at 110 K is shown in Fig. 6 and is correlated with sample resistance that also changes once AS occurs [31,20]. However, the peak almost totally recovers after magnetic field release (Fig.…”

Section: A Resonant X-ray Scatteringmentioning

confidence: 78%

“…We have performed extensive studies of the AS phenomenon by magnetism-oriented experiments [17][18][19][20] and by resistivity experiments [31]. It was demonstrated [18] that not only the magnetic but also the crystallographic c M axis is forced in this particular direction.…”

Section: B Easy Axis Switchingmentioning

confidence: 99%

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Magnetic field induced structural changes in magnetite observed by resonant x-ray diffraction and Mössbauer spectroscopy

Kołodziej¹,

Bialo

Tabiś

et al. 2020

Phys. Rev. B

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When a magnetic field is applied to a single crystal of magnetite at 124 K > T > 50 K, the monoclinic c M axis, which is the easy magnetization axis, switches to one of the 100 cubic directions, nearest to the direction of the magnetic field, and the phenomenon known as an axis switching (AS) occurs. A global symmetry probe, resonant x-ray scattering, and a local probe, Mössbauer spectroscopy, are used to better understand the mechanism of axis switching. The behavior of three subsystems ordered below the Verwey transition temperature T V , i.e., lattice distortion, an orbital, and charge orderings, was observed via resonant x-ray scattering as a function of an external magnetic field. This was preceded by calculation of selected peak intensities using the FDMNES code. The Mössbauer spectroscopy studies confirmed that the magnetic field triggers electronic rearrangements and atomic displacements. The structure observed after the process of axis switching is very similar to the one obtained after cooling below T V with the magnetic field applied along one of the initial 100 cubic directions and distinct from the cooling in the absence of a magnetic field. From all the experimental observations of the phenomenon done so far, it is clear that AS starts from the fluctuations between octahedral iron orbitals that ultimately lead to the Verwey transition, but also to the higher-temperature trimeron dynamics. Therefore, further observation of the axis switching may be a key point to the understanding of a majority of strongly correlated electronic behavior in magnetite as well as in other transition metal oxides.

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“…The iron oxide nanoparticle is an FCC-ordered ferrimagnetic ensemble of iron and oxygen atoms, where the net magnetization per lattice unit is given by 8 Iron atoms occupying octahedral sites 35 , 36 . Due to the magnetocrystalline anisotropy arising from spin-spin coupling, the iron magnetic moments tend to be preferentially aligned (above the Vervey transition temperature) along the [111] crystal axis and its eight geometrical equivalents for a cubic lattice 37 , 38 . Moreover, below a certain material dependent size, these magnetic moments are arranged in a single domain 39 , 40 and behave collectively as a single magnetic dipole.…”

Section: Resultsmentioning

confidence: 99%

Coupling a Single Nitrogen-Vacancy Center in Nanodiamond to Superparamagnetic Nanoparticles

Sadzak

Héritier

Benson

2018

Sci Rep

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Single nitrogen-vacancy (NV) defect centers in diamond have been exploited as single photon sources and spin qubits due to their room-temperature robust quantum light emission and long electron spin coherence times. They were coupled to a manifold of structures, such as optical cavities, plasmonic waveguides, and even injected into living cells to study fundamental interactions of various nature at the nanoscale. Of particular interest are applications of NVs as quantum sensors for local nanomagnetometry. Here, we employ a nanomanipulation approach to couple a single NV center in a nanodiamond to a single few-nm superparamagnetic iron oxide nanoparticle in a controlled way. After measuring via relaxometry the magnetic particle spin-noise, we take advantage of the crystal strain ms = ± 1 spin level separation to detect the superparamagnetic particle’s effect in presence of a driving AC magnetic field. Our experiments provide detailed insight in the behavior of such particles with respect to high frequency fields. The approach can be extended to the investigation of increasingly complex, but controlled nanomagnetic hybrid particle assemblies. Moreover, our results suggest that superparamagnetic nanoparticles can amplify local magnetic interactions in order to improve the sensitivity of diamond nanosensors for specific measurement scenarios.

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Magnetoresistance in magnetite: Switching of the magnetic easy axis

Cited by 7 publications

References 9 publications

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Magnetic field induced structural changes in magnetite observed by resonant x-ray diffraction and Mössbauer spectroscopy

Coupling a Single Nitrogen-Vacancy Center in Nanodiamond to Superparamagnetic Nanoparticles

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