Detailed analysis of spin-dependent quantum interference effects in magnetic tunnel junctions with Fe quantum wells

Abstract

We investigated spin-dependent quantum interference effects in Cr(001)/wedge Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions by dI/dV measurements. dI/dV intensities were mapped two-dimensionally as a function of applied voltage and Fe thickness, indicating a clear signature of quantum well (QW) states in the ultrathin Fe (001) electrode. However, resonant positions of QW states were systematically shifted by one monolayer when compared with the first-principles calculation results. X-ray absorption spectroscopy and magnetic circular dichroism measurements were also performed. While Fe oxide presence at Fe/MgO interface was ruled out, Fe/Cr intermixing could not be excluded. Hence, controlling the Fe/Cr interface may affect QW state.

Long-Range Phase Coherence in Double-Barrier Magnetic Tunnel Junctions with a Large Thick Metallic Quantum Well

“…In these structures, the QW potential barrier can be formed either by metallic layer using the symmetry dependent band structure [8][9][10][11][12][13], or by a double oxide tunneling barriers with a much greater barrier height for better electron confinement [14][15][16]. As so far, to preserve a good phase coherence, the metallic QW thickness in double barrier magnetic tunnel junctions (DMTJs) has been limited to around 1-2nm.…”

The effect of the MgO buffer layer thickness on magnetic anisotropy in MgO/Fe/Cr/MgO buffer/MgO(001)

“…38 The presence of intermixing at the Fe/Cr interface has been suggested in previous studies. 39 To clarify this issue, the elemental composition of MgO/Fe/Cr/MgO with an Fe thickness of 1.5 nm and an MgO thickness of 3 nm was studied by electron energy loss spectroscopy (EELS). High-angle annular dark field scanning transmission electron microscopy (HAADF STEM) images and the EELS spectra were collected using the JEM-ARM200F microscope operating at 200 kV in the STEM mode.…”

Tunnel magnetoresistance and spin transfer torque in magnetic tunnel junction with embedded nanoparticles

“…Note that T || has the maximum value when the direction of the magnetic moment of the nanoparticle follows the direction (or coincides with the direction) of the magnetization of the lower FM layer. Due to the identical determination of the spin-polarized current in single-barrier MTJ and in MTJ with nanoparticles during ballistic tunneling of electrons, in both cases the parallel STT component was calculated in a similar way using the equation (5). Figure 5 shows the dependence of T || on the applied voltage for MTJ with nanoparticles in different states (see curves 1-3) and for a single-barrier MTJ (see curve 4).…”

“…Double barrier MTJs are promising structures for MRAM applications due to better thermal stability, low noise and less critical current value for the switching in comparison to single barrier tunnel junctions (SMTJs) [1]. Moreover, both DMTJ and MTJ-NPs show a different spin-dependent quantum effects on ferromagnet/barrier and metallic (or magnetic) NP/barrier interfaces, which can be related to Coulomb blockade (CB), quantum well (QW) states, ballistic tunneling, resonant spin filtering and Kondo effect depending on middle layer thickness and applied voltage [2][3][4][5][6][7].…”