Abstract
Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena. Here we show that, in contrast to this common expectation, spin-independent conductance in compensated antiferromagnets and normal metals can be efficiently exploited in spintronics, provided their magnetic space group symmetry supports a non-spin-degenerate Fermi surface. Due to their momentum-dependent spin polarization, such antiferromagnets can be used as active elements in antiferromagnetic tunnel junctions (AFMTJs) and produce a giant tunneling magnetoresistance (TMR) effect. Using RuO2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO2/TiO2/RuO2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO2 electrodes, resulting in the TMR effect as large as ~500%. These results are expanded to normal metals which can be used as a counter electrode in AFMTJs with a single antiferromagnetic layer or other elements in spintronic devices. Our work uncovers an unexplored potential of the materials with no global spin polarization for utilizing them in spintronics.
Highlights
Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena
We embark on a different path and argue that globally spin-independent conductance in compensated antiferromagnets can be efficiently used in spintronics, provided their crystal symmetry supports a non-spin-degenerate Fermi surface and momentum-dependent spin polarization
While such a spin polarization is cancelled out in the net conductance due to being antisymmetric with respect to certain symmetry operations, its presence in the momentum space can be functionalized if such an antiferromagnet is combined with another similar antiferromagnet in a spintronic device such as an antiferromagnetic tunnel junctions (AFMTJs)
Summary
Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena. Using RuO2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO2/TiO2/RuO2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO2 electrodes, resulting in the TMR effect as large as ~500%. These results are expanded to normal metals which can be used as a counter electrode in AFMTJs with a single antiferromagnetic layer or other elements in spintronic devices. These considerations can be expanded to normal (nonmagnetic) metals with spin-orbit coupling where the combined space inversion-time reversal symmetry is broken, indicating that they can be utilized in spintronics despite globally spin-neutral currents
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