Possible influence of electron — lattice interactions on the Verwey transition in magnetite

Following the controversy between two previous publications (Lorenzo et al 2008 Phys. Rev. Lett. 101 226401 and Garcia et al 2009 Phys. Rev. Lett. 102 176405), we report on the influence of mechanical polishing, and subsequent sample storage, on the electronic order at the Verwey transition of highly pure magnetite, Fe(3)O(4), by resonant x-ray scattering. Contrary to expectations, mechanically polishing the surface induces an inhomogeneous micron deep dead layer, probably of powdered Fe(3)O(4). In addition, we have found that polishing the sample immediately before the experiment influences and favors the appearance of long range order electronic correlations, whereas samples polished well in advance have their electronic order quenched. Conversely, lattice distortions associated with the Verwey transition appear less affected by the surface state. We conclude that mechanical polishing induces stresses at the surface that may propagate into the core of the single crystal sample. These strains relax with time, which affects the different order parameters, as measured by x-ray resonant diffraction.

Section: Zn-doped and Non-stoichiometric Fe 3 Osupporting

confidence: 62%

Effect of surface polishing and oxidization induced strain on electronic order at the Verwey transition in Fe₃O₄

Tabiś¹,

Lorenzo²,

Kozłowski³

et al. 2013

“…With decreasing temperature is reduced and below RT the population of the excited state leads to a notable change in the temperature dependence of the anisotropy, resulting in the reversal of the sign of K 1 at the spin reorientation transition. At the Verwey transition becomes zero, components of the degenerate state transform to Cc crystallographic domains with considerable macroscopic distortion, the degeneracy is The strong temperature dependence of may be reflected in the behavior of the elastic constants, the strong temperature variation of which was reported by Ka ¸kol and Kozłowski [24].…”

Section: Discussionmentioning

confidence: 87%

Magnetocrystalline anisotropy of magnetite

Řezníček

Chlan

Štěpánková

et al. 2012

The spin reorientation temperature T(SR) of stoichiometric Fe(3)O(4), as well as of magnetite with a small number of vacancies and magnetite containing a low concentration of Ti, Zn, Al and Ga was measured on single-crystal samples using the ac susceptibility. In the same experiment the temperature T(V) of the Verwey transition was also found. The results show that a correlation between T(SR) and T(V) exists. The electronic structure of the compounds studied was determined using the density-functional-based GGA + U method. For stoichiometric magnetite the first and second cubic anisotropy constants were calculated, while for magnetite with defects the distribution of electron density using the 'atoms in molecules' approach was determined. Based on a combination of experimental results with the electronic structure calculations an explanation of the temperature dependence of the magnetocrystalline anisotropy of magnetite is suggested.

“…Clearly, in order to obtain higher-order accuracy-concerning quantitative results of system parameters, conductivity and ionic ordering-all relevant interactions are to be cared for, as recently pointed out with regard to the kinetic electron energy (hopping-integral T ik ), mainly under theoretical band structure aspects, by Mishra et al [245] and with respect to electron-phonon interactions, from an experimental point of view, by Kakol et al [246], cf section 3.3.3. The successful Coulomb approach of Brabers et al [237][238][239], however, supports the relative role assigned to the various interactions, in terms of the Ihle-Lorenz conception [166].…”

Section: Progress In Theoretical Model Designing (Since 1979)mentioning

confidence: 99%

The Verwey transition - a topical review

Walz¹

2002

700

651

This review encompasses the story of the Verwey transition in magnetite over a period of about 90 years, from its discovery up to the present. Despite this long period of thorough investigation, the intricate multi-particle system Fe3O4 with its various magneto-electronic interactions is not completely understood, as yet - although considerable progress has been achieved, especially during the last two decades. It therefore appeared appropriate to subdivide this retrospect into three eras: (I) from the detection of the effect to the Verwey model (1913-1947), being followed by a period of: (II) checking, questioning and modification of Verwey's original concepts (1947-1979). Owing to prevailing under-estimation of the role of crystal preparation and qualitiy control, this period is also characterized by a series of uncertainties and erroneous statements concerning the reaction order (one or two) and type of the transition (multi-stage or single stage). These latter problems, beyond others, could definitely be solved within era (III) (1979 to the present) - in favour of a first-order, single-stage transition near 125 K - on the basis of experimental and theoretical standards established in the course of a most inspiring conference organized in 1979 by Sir Nevill Mott in Cambridge and solely devoted to the present topic. Regarding the experimental field of further research, the remarkable efficiency of magnetic after-effect (MAE) spectroscopy as a sensitive probe for quality control and investigation of low-temperature (4 KTv) into a Wigner crystal (T