Probing One Antiferromagnetic Antiphase Boundary and Single Magnetite Domain Using Nanogap Contacts

Abstract

We have probed one antiferromagnetic (AF) antiphase boundary (APB) and a single Fe(3)O(4) domain using nanogap contacts. Our experiments directly demonstrate that, in the case of probing one AF-APB, a large magnetoresistance (MR), high resistivity, and a high saturation field are observed as compared with the case of probing a single Fe(3)O(4) domain. The shape of the temperature-dependent MR curves is also found to differ between the single domain and one of the AF-APB measurements, with a characteristic strong temperature dependence for the single domain and temperature independence for the one AF-APB case. We argue that these observations are indicative of profound changes in the electronic transport across APBs. The investigated APB defects increase the activation energy and disturb the long-range charge ordering of monodomain Fe(3)O(4).

Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films

“…28,29 The presence of anti-phase boundary defects in Fe 3 O 4 contribute to its unusual magnetic and transport properties, such as the magnetization non-saturation even at very high field, 30,31 the super-paramagnetic behavior in Fe 3 O 4 films, 32,33 and a greater MR response across the AF-APBs. [34][35][36] On the other hand, in polycrystalline Fe 3 O 4 thin films, interesting properties such as magnetic-transport, 37 spin-injection, 38 and charge ordering 39,40 have also been investigated and discussed. Therefore, it is worth investigating the magnetic properties of stepped epitaxial Fe 3 O 4 films produced on large miscut angle vicinal MgO substrates, as a high density APBs is expected along the step edges.…”

“…36,42 If APB density along the step edges is higher than perpendicular to steps, the resistivity measured along the step edges should be higher than that measured perpendicular to steps. To confirm this, we studied the local transport properties of 60 nm thick stepped Fe 3 O 4 films using sub-100 nm nano-gap contacts.…”

Transversal magneto-resistance in epitaxial Fe3O4 and Fe3O4/NiO exchange biased system

“…This system presents anti-phase boundaries (APB), they are defects naturally arising due to the difference in rotational and translational symmetry between substrate and thin film. [24][25][26][27][28] The APBs dominate the transport properties in thin films due to the predominantly antiferromagnetic (AF) exchange they induce. 27,28 In this letter, we have investigated the dependence of the transversal MR on the bias current in epitaxial Fe 3 O 4 and Fe 3 O 4 /NiO exchange biased system.…”

Anomalous magnetization reversal due to proximity effect of antiphase boundaries

“…[5][6][7] Studies of epitaxial thin films and heterostructures containing APBs have attracted considerable attention during the last decade as APBs can significantly alter the physical properties of thin films, which is advantageous for the development of spintronic devices. [8][9][10][11] One of the important epitaxial heterostructures for these studies is Fe 3 O 4 thin films grown on MgO substrates. Since the Fe 3 O 4 (F d3m) crystal structure is lower in symmetry than MgO (F m3m) there are several equivalent nucleation sites on the MgO surface, which enforce the formation of APBs at the junctions of neighboring grains.…”

“…The domain sizes calculated for our (110) oriented films are found to be on average 9.7% smaller than the corresponding domain sizes reported in the case of (100) oriented films for the same film thickness. 19 By considering that around 20-30% of APBs are AF-APBs 11,25 and the mean domain size of our (110) oriented films is significantly smaller than in the case of (100) oriented films, we can consider the possibility of exchange coupling of neighboring magnetic domains through AF-APBs. For a greater understanding let us consider a simplified situation, where two magnetic domains of different size, large domain (L), and small domain (S) are exchange coupled through the in-plane AF-APBs.…”