Magnetic and structural studies of magnetite at the Verwey transition

Tabiś, Wojciech; Tarnawski, Z.; Ka̧kol, Z.; Król, G.; Kołodziejczyk, Andrzej; Kozłowski, A.; Fluerasu, Andrei; Honig, J. M.

doi:10.1016/j.jallcom.2006.08.357

Cited by 8 publications

(6 citation statements)

References 12 publications

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“…We note here that, although AC susceptibility is a magnetic parameter, it shows the changing electronic system as described in [23]; the structural changes are reflected by (1 1½ 2) peak (absent in high T cubic phase). The present studies constitute an extension of the previous experiments [24], where both AC susceptibility and the resistivity were traced the same way.…”

Section: How the Transition Proceedsmentioning

confidence: 59%

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: How the Transition Proceedsmentioning

confidence: 59%

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 kinks at around 120-140 K can be attributed to the Verwey transition, which is usually related to the presence of stoichiometric magnetite (Fe 3 O 4 ). 54,55 The existence of such crystal phase in relevant proportions is indeed expected for relatively large IO nanoparticles (4 10-12 nm), for which incomplete oxidation results in an inner ''core'' made of the less oxidized magnetite (i.e., Fe 3 O 4 ) and an outer layer of the more oxidized maghemite (i.e., g-Fe 2 O 3 ). [49][50][51][52][53][54][55] Moreover, it should be considered that the size distributions of the IO domains are relatively broad and quasi-bimodal for the investigated HNCs decorated with the larger IO domains (Fig.…”

Section: Magnetic Properties Of the Hncsmentioning

confidence: 89%

Colloidal semiconductor/magnetic heterostructures based on iron-oxide-functionalized brookite TiO2 nanorods

Buonsanti

Snoeck

Giannini

et al. 2009

Phys. Chem. Chem. Phys.

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A flexible colloidal seeded-growth strategy has been developed to synthesize all-oxide semiconductor/magnetic hybrid nanocrystals (HNCs) in various topological arrangements, for which the dimensions of the constituent material domains can be controlled independently over a wide range. Our approach relies on driving preferential heterogeneous nucleation and growth of spinel cubic iron oxide (IO) domains onto brookite TiO2 nanorods (b-TiO2) with tailored geometric parameters, by means of time-programmed delivery of organometallic precursors into a suitable TiO2-loaded surfactant environment. The b-TiO2 seeds exhibit size-dependent accessibility towards IO under diffusion-controlled growth regime, which allows attainment of HNCs individually made of a single b-TiO2 section functionalized with either one or multiple nearly spherical IO domains. In spite of the dissimilarity of the respective crystal-phases, the two materials share large interfacial junctions without significant lattice strain being induced across the heterostructures. The synthetic achievements have been supported by a systematic morphological, compositional and structural characterization of the as-prepared HNCs, offering a mechanistic insight into the specific role of the seeds in the control of heterostructure formation in liquid media. In addition, the impact of the formed b-TiO2/IO heterojunctions on the magnetic properties of IO has also been assessed.

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“…6). Magnetite shows a magnetic phase transition at a temperature close to 120 K, known as the Verwey magnetic transition (Gridin et al, 1996;Tarnawski et al, 2004;Tabiś et al, 2007), thus reinforcing the attribution of the 120 K effect to extremely diluted magnetite inclusions and involving only a minor part of the sample and not consequently justifying a variation in heat capacity.…”

Section: -------------Sample Pba90-94 -------------Tetrahedral Bond Lmentioning

confidence: 76%

Magnetic behaviour of trioctahedral mica-2M1 occurring in a magnetic anomaly zone

Pini¹,

Affronte²,

Brigatti³

2008

Mineral. mag.

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This work relates the crystal chemistry and the magnetic behaviour of a trioctahedral mica (chemical formula: (K0.90Na0.01Ca0.01Ba0.01 ☐0.07)(Al0.05Fe2+1.10Mg1.38Ti0.32Mn0.01☐0.04)(Al1.12Si2.88)O10 (F0.27OH1.27O0.46); unit cell parameters: a = 5.345(2) Å, b = 9.261(4) Å, c = 20.189(8) Å; β = 95.075(8)°) from Minto Block (Ungava peninsula, northern Quebec, Canada), a region characterized by high magnetic anomalies. Crystallographic and X-ray absorption spectroscopy data suggest a prevalent divalent oxidation state for Fe and a disordered Fe 2+ distribution in the two octahedral sites Ml and M2. The real part of magnetic susceptibility shows two peaks at ∼5.2 K and 120 K. However, as demonstrated by AC magnetic susceptibility measurements, the origin of the two effects is different: the peak position of the first one (i.e. the effect revealed at 5.2 K) is frequency-dependent, thus suggesting a spin-glass like behaviour. The effect at 120 K can instead be attributed to the occurrence of diluted phases in mica matrix, such as Fe oxides.

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Magnetic and structural studies of magnetite at the Verwey transition

Cited by 8 publications

References 12 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

Colloidal semiconductor/magnetic heterostructures based on iron-oxide-functionalized brookite TiO2 nanorods

Magnetic behaviour of trioctahedral mica-2M1 occurring in a magnetic anomaly zone

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