Magnetocrystalline Anisotropy of Low Temperature Phase of Magnetite

Abe, Kouji; Miyamoto, Yoko; Chikazumi, S.

doi:10.1143/jpsj.41.1894

Cited by 164 publications

(109 citation statements)

References 17 publications

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“…At this intrinsic transition, magnetite undergoes a structural change from cubic to monoclinic with a shift of the easy axes from [111] to [100], which causes a prominent change in the magnetization properties [41 -45]. The switching of the magnetic axes is associated with an increase of jK 1 j as calculated from monoclinic anisotropy constants and a decrease of magnetization [43,46,47]. Considering the chain configuration in MTB, the switching of easy axes from [111] to [100] weakens the net magnetic moment of the chains and randomizes their contribution to B int .…”

Section: Experimental Set-upmentioning

confidence: 99%

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S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

Gehring

Kind

Charilaou

et al. 2013

J. R. Soc. Interface.

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We report the use of S-band ferromagnetic resonance (FMR) spectroscopy to compare the anisotropic properties of magnetite particles in chains of cultured intact magnetotactic bacteria (MTB) between 300 and 15 K with those of sediment samples of Holocene age in order to infer the presence of magnetofossils and their preservation in a geological time frame. The spectrum of intact MTB at 300 K exhibits distinct uniaxial anisotropy because of the chain alignment of the cellular magnetite particles and their easy axes. This anisotropy becomes less pronounced upon cooling and below the Verwey transition (T V ) it is nearly vanished mainly owing to the change of direction of the easy axes. In a natural sample, magnetofossils were detected by uniaxial anisotropy traits similar to those obtained from cultured MTB above T V . Our comparative study emphasizes that indispensable information can be obtained from S-band FMR spectra, which offers even a better resolution than X-band FMR for discovering magnetofossils, and this in turn can contribute towards strengthening our relatively sparse database for deciphering the microbial ecology during the Earth's history.

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Section: Experimental Set-upmentioning

confidence: 99%

“…The decrease of the signals below 80 K can be explained by the large monoclinic anisotropy constants [46] that hamper the alignment of the magnetization vector along the external magnetic field ( figure 1a). This, in turn, causes reduction of the FMR intensity, as discussed in §2.1.…”

Section: Experimental Set-upmentioning

confidence: 99%

S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

Gehring

Kind

Charilaou

et al. 2013

J. R. Soc. Interface.

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“…Compared to single domain assemblages of the same mineralogy, superparamagnetic crystals of will have narrower linewidths (small ∆B), nearly symmetric absorption (A ~ 1), and g eff closer to the mineral's g-factor [17,18]. Superparamagnetic assemblages of magnetites will show broader, more asymmetric linewidths (e.g, larger ∆B and A farther from 1) and higher g eff at 77 K compared to room temperature (e.g., [19,20]). However, because FMR absorption and linewidth are smooth functions of particle size with no discontinuities across the single domain superparamagnetic boundary, there is no concept of "blocking temperature" in FMR [9].…”

Section: Dependence Of Fmr On Crystal Sizementioning

confidence: 99%

Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite

Weiss

Kim

Kirschvink

et al. 2004

Earth and Planetary Science Letters

156

222

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“…Above T V , in contrast, crystal structure analysises show no evidence of the lowered symmetry from the cubic one, apparently contradicting with our prediction of the ferro-OO even in the metallic phase. However, the symmetry in the electronic structure has been pointed out to be lowered than the cubic one [30] based on magneto-crystalline anisotropy measurements [31] and in the recent resonant X-ray scattering at room temperature [13], consistent with the OO state.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

Aspects of the Verwey transition in magnetite

2002

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A new mechanism of the Verway transition in magnetite (Fe 3 O 4 ), which has been argued to be a charge ordering transition so far, is proposed. Based on the mean field calculations for the three band model of spinless fermions appropriate for the d electrons of the Fe ions on the B sites, it is indicated that the phase transition should be the bond dimerization due to the cooperative effects of strong electronic correlation and electron-phonon interaction. The results show that the ferro-orbital ordered state is stabilized in a wide temperature range due to the strong on-site Coulomb interaction between different t 2g orbitals resulting in an effectively one-dimensional electronic state, which leads the system toward an insulating state by the Peierls lattice distortion with the period of two Fe(B) ions, i.e., bond dimerization. Furthermore, it is found that the interplay between such lattice distortion in the Fe(B) ions and the lattice elastic energy of the Fe(B)-O as well as the Fe(A)-O bonds gives rise to a competition between two different three-dimensional patterns for the bond dimerization, and can stabilize a complicated one with a large unit cell size. The results are compared with the known experimental facts.

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Magnetocrystalline Anisotropy of Low Temperature Phase of Magnetite

Cited by 164 publications

References 17 publications

S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite

Aspects of the Verwey transition in magnetite

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