Anisotropic magnetoresistance across Verwey transition in charge ordered Fe3O4 epitaxial films

Abstract

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.

A Short Review on Verwey Transition in Nanostructured Fe3O4 Materials

“…The anisotropic magnetoresistance (AMR) of highquality epitaxial Fe 3 O 4 films on MgO (100) and Al 2 O 3 (0001) substrates [36] was investigated in charge-ordering state, as shown in Figure 7(a). It was found that the Verwey transition contains two processes, a fast charge-ordering process and a continuous formation of trimeron process.…”

Magnetoresistance of epitaxial and polycrystalline Fe3O4 films near Verwey transition

“…The details of fabrication have been published elsewhere. 26 The film thickness of about 200 nm was determined using a Dektak 6M surface profiler and by transition electron microscopy (TEM). Stoichiometry of Fe 3(1-d) O 4 thin films with d less than 3.5 Â 10 À4 was determined by Rutherford backscattering spectroscopy with the precision of 10 À3 -10 À2 at.…”

“…%. 26 Electronic transport properties of Fe 3 O 4 films were measured using the standard four-probe method using a Quantum Design physical property measurement system. The and Fe 3 O 4 /quartz samples are 117.7, 122.8, and 122.4 K, respectively, which are decided by the maximum slope of logq [see Fig.…”

“…We suppose that the high density APBs impact the electronic transport mechanism above T V and obscure the dependence of the mechanism of MR on temperature. Different electronic transport mechanisms in Fe 3 O 4 may respond for the temperature-dependent mechanism of MR. 26,29 Electronic microscopic studies have manifested the existence of twin boundaries below T V . [23][24][25] However, Eq.…”

Anomalous electric transport across Verwey transition in nanocrystalline Fe3O4 thin films

“…However, there still exist uncertainties as to the precise mechanism responsible for this electrical and structural transition. Further, the consequential influence of magnetic properties on the transition and its electronic characteristic is still unclear, [7][8][9][10] particularly for nanocrystalline Fe 3 O 4 films.…”