Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer

Abstract

We have investigated the interlayer exchange coupling between the epitaxial spinel Fe 3 O 4 layers across an insulating nonmagnetic MgO spacer. The epitaxial structure used for these investigations was Fe 3 O 4 ͑10 nm͒ / MgO ͑0.8-3 nm͒ / Fe 3 O 4 ͑10 nm͒ / NiO ͑15 nm͒ multilayers grown on MgO ͑100͒ substrates. We find that the two Fe 3 O 4 layers are antiferromagnetic coupled through the MgO spacer when the MgO thickness is less than 1.5 nm. Furthermore, ab initio calculation of IEC for Fe/ MgO / Fe indicates the importance of electrode states, in particular, partial oxidation of the ferromagnetic electrodes.

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

“…[14][15][16] Recently, interesting magnetic and transport properties in epitaxial Fe 3 O 4 have been reported, i.e., magnetism in nanometerthick magnetite, 17 large orbital moment in nanoscale magnetite, 18 giant magnetization in nanometer-thick magnetite, 19 a spin Seebeck effect, 20 a spin filter effect, 21 electrical fieldinduced phase transition, [22][23][24] large transversal magnetoresitance (MR), 25,26 and spin valve effect. [27][28][29] However, initial efforts in exploiting its half metallic nature in magnetic tunnel junctions (MTJ) have been far from promising. 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.…”

“…[27][28][29] However, initial efforts in exploiting its half metallic nature in magnetic tunnel junctions (MTJ) have been far from promising. 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.…”

Antiferromagnetic coupling and impurity effects at junctions betweenFe3O4and Fe(001) layers

“…The availability of the state-of-the-art technology of thin-film preparation combined with new theoretical insights has led to the discovery of various fascinating phenomena, such as two-dimensional high-mobility carriers [4] and interlayer exchange coupling (IEC) [5][6][7][8], including exchange bias [9]. Among the various oxide films, the perovskite family has been known to exhibit remarkable interfacial phenomena, whereas studies on spinel ferrite films and devices based on such films are relatively fewer than those on the perovskite films, probably due to the difficulties in controlling the spinel ferrite film quality, the complexity of the crystal structure, etc.…”

Anomalous magnetization reversal due to proximity effect of antiphase boundaries

“…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. It is clear that the AF-APBs induce an AF interfacial exchange coupling 26 which increases the critical field of small size domains and decreases the critical field of the large size domains causing the double switching in HLs. Please note that the AF exchange coupling in the referred paper is through an MgO barrier layer, 26 while, in our case, the AF exchange coupling is through AF-APBs.…”

“…It is clear that the AF-APBs induce an AF interfacial exchange coupling 26 which increases the critical field of small size domains and decreases the critical field of the large size domains causing the double switching in HLs. Please note that the AF exchange coupling in the referred paper is through an MgO barrier layer, 26 while, in our case, the AF exchange coupling is through AF-APBs. The spin configurations at different stages of the hysteresis loop are shown schematically in the inserts of Fig.…”