2 research outputs found
Nonlinear terahertz N\'eel spin-orbit torques in antiferromagnetic MnAu
Antiferromagnets have large potential for ultrafast coherent switching of
magnetic order with minimum heat dissipation. In novel materials such as
MnAu and CuMnAs, electric rather than magnetic fields may control
antiferromagnetic order by N\'eel spin-orbit torques (NSOTs), which have,
however, not been observed on ultrafast time scales yet. Here, we excite
MnAu thin films with phase-locked single-cycle terahertz electromagnetic
pulses and monitor the spin response with femtosecond magneto-optic probes. We
observe signals whose symmetry, dynamics, terahertz-field scaling and
dependence on sample structure are fully consistent with a uniform in-plane
antiferromagnetic magnon driven by field-like terahertz NSOTs with a torkance
of (15050) cm/A s. At incident terahertz electric fields above 500
kV/cm, we find pronounced nonlinear dynamics with massive N\'eel-vector
deflections by as much as 30{\deg}. Our data are in excellent agreement with a
micromagnetic model which indicates that fully coherent N\'eel-vector switching
by 90{\deg} within 1 ps is within close reach.Comment: 16 pages, 4 figure
Optically-triggered strain-driven N\'{e}el vector manipulation in a metallic antiferromagnet
The absence of stray fields, their insensitivity to external magnetic fields,
and ultrafast dynamics make antiferromagnets promising candidates for active
elements in spintronic devices. Here, we demonstrate manipulation of the
N\'{e}el vector in the metallic collinear antiferromagnet MnAu by combining
strain and femtosecond laser excitation. Applying tensile strain along either
of the two in-plane easy axes and locally exciting the sample by a train of
femtosecond pulses, we align the N\'{e}el vector along the direction controlled
by the applied strain. The dependence on the laser fluence and strain suggests
the alignment is a result of optically-triggered depinning of 90
domain walls and their sliding in the direction of the free energy gradient,
governed by the magneto-elastic coupling. The resulting, switchable, state is
stable at room temperature and insensitive to magnetic fields. Such an approach
may provide ways to realize robust high-density memory device with switching
timescales in the picosecond range