Magnetic and Electric Properties of Magnetite at Low Temperatures

Calhoun, B. A.

doi:10.1103/physrev.94.1577

Cited by 215 publications

(80 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A similar concept has been applied recently to explain the dynamic conductivity at the metal-insulator transition in quasi-one-dimensional ␤-Na 0.33 V 2 O 5 . 17 At low temperatures the conduction in magnetite takes place via hopping between localized states, which agrees well with both activated dc resistivity [18][19][20] and with an observed characteristic power law ϰ s ͑Ref. 21͒ of the ac conductivity.…”

Section: Introductionsupporting

confidence: 66%

Terahertz conductivity at the Verwey transition in magnetite

et al. 2005

View full text Add to dashboard Cite

The complex conductivity at the (Verwey) metal-insulator transition in Fe3O4 has been investigated at THz and infrared frequencies. In the insulating state, both the dynamic conductivity and the dielectric constant reveal a power-law frequency dependence, the characteristic feature of hopping conduction of localized charge carriers. The hopping process is limited to low frequencies only, and a cutoff frequency ν1 ≃ 8 meV must be introduced for a self-consistent description. On heating through the Verwey transition the low-frequency dielectric constant abruptly decreases and becomes negative. Together with the conductivity spectra this indicates a formation of a narrow Drude-peak with a characteristic scattering rate of about 5 meV containing only a small fraction of the available charge carriers. The spectra can be explained assuming the transformation of the spectral weight from the hopping process to the free-carrier conductivity. These results support an interpretation of Verwey transition in magnetite as an insulator-semiconductor transition with structure-induced changes in activation energy.

show abstract

Section: Introductionsupporting

confidence: 66%

Terahertz conductivity at the Verwey transition in magnetite

et al. 2005

View full text Add to dashboard Cite

show abstract

“…Below T V , the easy axis turns to [001] m [18]. The monoclinic Cc structure can form up to 24 orientations with six equal probabilities of c axis orientation during zero-field cooling [26,27]. When the magnetic field is along one of the cubic 001 directions, the c axis can be aligned during field cooling above 1000 Oe [26].…”

Section: Resultsmentioning

confidence: 99%

Anisotropic magnetoresistance across Verwey transition in charge ordered Fe3O4 epitaxial films

Liu

Zhang

et al. 2017

Phys. Rev. B

View full text Add to dashboard Cite

The anisotropic magnetoresistance (AMR) near the Verwey temperature (T V ) is investigated in charge ordered Fe 3 O 4 epitaxial films. When the temperature continuously decreases below T V , the symmetry of AMR in Fe 3 O 4 (100) film evolves from twofold to fourfold at a magnetic field of 50 kOe, where the magnetic field is parallel to the film surface, whereas AMR in Fe 3 O 4 (111) film maintains twofold symmetry. By analyzing AMR below T V , it is found that the Verwey transition contains two steps, including a fast charge ordering process and a continuous formation process of trimeron, which is comfirmed by the temperature-dependent Raman spectra. Just below T V , the twofold AMR in Fe 3 O 4 (100) film originates from uniaxial magnetic anisotropy. The fourfold AMR at a lower temperature can be ascribed to the in-plane trimerons. By comparing the AMR in the films with two orientations, it is found that the trimeron shows a smaller resistivity in a parallel magnetic field. The field-dependent AMR results show that the trimeron-sensitive field has a minimum threshold of about 2 kOe.

show abstract

“…The cubic phase has an activation energy of about 62 meV while the orthorhombic phase has an activation energy of about 105 meV. Calhoun (1954) reported activation energies of 30 meV and 110 meV, respectively. The difference in the conductivity and activation energies is not believed to be due to impurities in our samples.…”

Section: Resistivitymentioning

confidence: 99%

“…The transition temperature was taken as the midpoint between the two conductivity regions and was found to be T, = 123 F 1 K, or about 4 K higher than reported for bulk magnetite (Calhoun 1954). …”

Section: Resistivitymentioning

confidence: 99%

“…Previous measurements of the electrical properties have been performed on crystalline or ceramic samples (Bickford 1953, Lavine 1959, Kostopoulos and Theodossiou 1970, Kostopoulos 1972, Siemons 1970, Drabble et a1 1971, Calhoun 1954and DomeniCali 1950. The conductivity has been measured from below 4 K to above the Curie temperature of 858 K. The extraordinary Hall effect has been measured on bulk samples from 77K to over 200°C (Lavine 1961, Kostopoulos andTheodossiou 1970).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Magnetoelectric properties of magnetite thin films

Feng¹,

Pashley²,

Nicolet³

1975

J. Phys. C: Solid State Phys.

View full text Add to dashboard Cite

Abstract. Resistivity, DC Hall effect and transverse magnetoresistance measurements were made on polycrystalline thin films of magnetite (Fe,OJ from 104 K to room temperature. The Verwey transition is observed at Tv = 123 K, about 4 K higher than reported for bulk magnetite. The ordinary and extraordinary Hall coefficients are negative over the entire temperature range, consistent with negatively charged carriers. The extraordinary Hall coefficient exhibits a dependence on the resistivity above Tv and a p2', dependence below Tv. The magnetoresistance is negative at all temperatures and for all magnetic field strengths. The planar Hall effect signal was below the sensitivity of the present experiment.

show abstract

Magnetic and Electric Properties of Magnetite at Low Temperatures

Cited by 215 publications

References 17 publications

Terahertz conductivity at the Verwey transition in magnetite

Terahertz conductivity at the Verwey transition in magnetite

Anisotropic magnetoresistance across Verwey transition in charge ordered Fe3O4 epitaxial films

Magnetoelectric properties of magnetite thin films

Contact Info

Product

Resources

About