Kavli Affiliate: Gregory D. Fuchs
| First 5 Authors: Jaimin Kang, Jaimin Kang, , ,
| Summary:
Magnetic tunnel junctions (MTJs) based on ferromagnets are canonical devices
in spintronics, with wide-ranging applications in data storage, computing, and
sensing. They simultaneously exhibit mechanisms for electrical detection of
magnetic order through the tunneling magnetoresistance (TMR) effect, and
reciprocally, for controlling magnetic order by electric currents through
spin-transfer torque (STT). It was long assumed that neither of these effects
could be sizeable in tunnel junctions made from antiferromagnetic materials,
since they exhibit no net magnetization. Recently, however, it was shown that
all-antiferromagnetic tunnel junctions (AFMTJs) based on chiral
antiferromagnets do exhibit TMR due to their non-relativistic
momentum-dependent spin polarization and cluster magnetic octupole moment,
which are manifestations of their spin-split band structure. However, the
reciprocal effect, i.e., the antiferromagnetic counterpart of STT driven by
currents through the AFMTJ, has been assumed non-existent due to the total
electric current being spin-neutral. Here, in contrast to this common
expectation, we report nanoscale AFMTJs exhibiting this reciprocal effect,
which we term octupole-driven spin-transfer torque (OTT). We demonstrate
current-induced OTT switching of PtMn3|MgO|PtMn3 AFMTJs, fabricated on a
thermally oxidized silicon substrate, exhibiting a record-high TMR value of
363% at room temperature and switching current densities of the order of 10
MA/cm2. Our theoretical modeling explains the origin of OTT in terms of the
imbalance between intra- and inter-sublattice spin currents across the AFMTJ,
and equivalently, in terms of the non-zero net cluster octupole polarization of
each PtMn3 layer. This work establishes a new materials platform for
antiferromagnetic spintronics and provides a pathway towards deeply scaled
magnetic memory and room-temperature terahertz technologies.
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