Influence of titanium doping on the magnetocrystalline anisotropy of magnetite

Ka̧kol, Z.; Sabol, J.; Stickler, J J; Kozłowski, A.; Honig, J.M.

doi:10.1103/physrevb.49.12767

Cited by 49 publications

(43 citation statements)

References 39 publications

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“…) and the Verwey transition observed for magnetite (Verwey ) and Ti‐poor titanomagnetite composition with less than 4% Ti (Kakol et al. ). The M S variation across the transition at 70 K is 0.10 Am 2 kg −1 (determined on a 30 mg sample), corresponding to 0.63 wt% of chromite, using a M S of 16 Am 2 kg −1 for pure chromite (Robbins et al.…”

Section: Intrinsic Magnetic Propertiesmentioning

confidence: 96%

Opaque minerals, magnetic properties, and paleomagnetism of the Tissint Martian meteorite

Gattacceca

Hewins

Lorand

et al. 2013

Meteorit & Planetary Scien

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Abstract-We present a description of opaque minerals, opaque mineral compositions, magnetic properties, and paleomagnetic record of the Tissint heavily shocked olivine-phyric shergottite that fell to Earth in 2011. The magnetic mineralogy of Tissint consists of about 0.6 wt% of pyrrhotite and 0.1 wt% of low-Ti titanomagnetite (in the range ulv€ ospinel 3-15 magnetite 85-97). The titanomagnetite formed on Mars by oxidation-exsolution of ulv€ ospinel grains during deuteric alteration. Pyrrhotite is unusual, with respect to other shergottites, for its higher Ni content and lower Fe content. Iron deficiency is attributed by an input of regolith-derived sulfur. This pyrrhotite has probably preserved a metastable hexagonal monosulfide solution structure blocked at temperature above 300°C. The paleomagnetic data indicate that Tissint was magnetized following the major impact suffered by this rock while cooling at the surface of Mars from a post-impact equilibrium temperature of approximately 310°C in a stable magnetic field of about 2 µT of crustal origin. Tissint is too weakly magnetic to account for the observed magnetic anomalies at the Martian surface.

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Section: Intrinsic Magnetic Propertiesmentioning

confidence: 96%

Opaque minerals, magnetic properties, and paleomagnetism of the Tissint Martian meteorite

Gattacceca

Hewins

Lorand

et al. 2013

Meteorit & Planetary Scien

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“…In pure stoichiometric magnetite, T K ≈ 120 K. Small amounts of impurity cations, e.g., Ti 4+ [ Kakol et al , 1992, 1994], Zn 2+ [ Kozlovski et al , 1995], and Al 3+ [ Kozlovski et al , 1996], lower the transition temperature, while Ti substitution beyond x = 0.04 causes the remanence transition to disappear [ Honig , 1995]. Nonstoichiometry has a similar effect.…”

Section: Introductionmentioning

confidence: 99%

Hallmarks of maghemitization in low‐temperature remanence cycling of partially oxidized magnetite nanoparticles

Özdemir¹,

Dunlop²

2010

J. Geophys. Res.

148

185

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[1] In environmental, soil, and sediment magnetism, it is important to be able to estimate the degree of oxidation of magnetite grains. We report a new method for finding the oxidation parameter z semiquantitatively from cooling-warming cycles of room temperature remanences. We measured magnetization M continuously for stoichiometric and partially oxidized magnetites with average grain sizes of 37 and 220 nm during zero-field cycling of 2.5 T saturation isothermal remanent magnetization (SIRM) from 300 K to 20 K and back to 300 K. Oxidized magnetites were obtained by heating stoichiometric magnetite in air at 100°C, 150°C, and 200°C. In other experiments, SIRM was given at 10 K, and M was monitored during zero-field warming to 300 K. In the oxidized magnetites, SIRM at first increases in cooling from 300 K and then decreases in approaching the Verwey transition. The hump-like form is even more pronounced in the warming curves above T V . For maghemite, the fully oxidized end member, we found reversible cooling-warming curves with no Verwey transition. In partially oxidized grains, consisting of a maghemite surface layer and a largely unoxidized core, a Verwey transition is resolvable up to high degrees of oxidation. Hallmarks of maghemitization include (1) a smeared-out Verwey transition shifted to lower temperatures when warming 20 K SIRM, (2) a shifted and broadened transition region in both cooling and warming of 300 K SIRM, and (3) humped cooling and warming curves of 300 K SIRM between 300 K and T V . Property 3 has excellent diagnostic value. It results from the combination of a slowly increasing M of maghemite and the rapid and nonlinear decrease in M of magnetite during cooling and is seen even for the slight initial oxidation of the reduced 37 nm magnetite. Certain properties, such as the change in M in warming from 20 K to T V and the change in initial and final M values in a complete cooling-warming cycle, are roughly proportional to the oxidation parameter z. However, the proportionality factors also depend on grain size d, which would have to be known independently in order to estimate z.Citation: Ö zdemir, Ö ., and D. J. Dunlop (2010), Hallmarks of maghemitization in low-temperature remanence cycling of partially oxidized magnetite nanoparticles,

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“…Further work determined that external magnetic fields influence the nature of the transition [ Williams et al , 1953] and that the magnetic response of the transition is highly sensitive to grain size and, thus, domain state [ Hodych , 1976; King and Williams , 2000; Kosterov , 2001; Moskowitz et al , 1993; Ozdemir et al , 1993]. Moreover, it was clearly established that oxidation state and cation substitution depress the transition temperature [ Aragón et al , 1985; Honig , 1995; Kąkol et al , 1994; Shepherd et al , 1991]. …”

Section: Introductionmentioning

confidence: 99%

Strain memory of the Verwey transition

Carporzen¹,

Gilder²

2010

J. Geophys. Res.

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[1] We studied the effects of stress on the Verwey transition for pure, stoichiometric, synthetic multidomain magnetite and for natural multidomain magnetite having both relatively low and high degrees of oxidation. Low-temperature measurements of the magnetic moments were carried out after pressure release. Our results unambiguously show an increase in the Verwey transition temperature with increasing pressure that ranges from 1 K/GPa for stoichiometric magnetite to 3 K/GPa for highly oxidized magnetite for pressures up to about 5 GPa. The transition width broadens with increasing stress for stoichiometric magnetite and then becomes less broad as oxidation increases until the width is invariant with respect to stress for highly oxidized magnetite. Heat treatment to 700°C does not appreciably reverse the effect, which could make the Verwey transition suitable for use as a geobarometer in cases where high pressures (>1 GPa) are involved, such as in meteorite impact craters. A model explaining the results is put forward.

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Influence of titanium doping on the magnetocrystalline anisotropy of magnetite

Cited by 49 publications

References 39 publications

Opaque minerals, magnetic properties, and paleomagnetism of the Tissint Martian meteorite

Opaque minerals, magnetic properties, and paleomagnetism of the Tissint Martian meteorite

Hallmarks of maghemitization in low‐temperature remanence cycling of partially oxidized magnetite nanoparticles

Strain memory of the Verwey transition

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