  The magnetic tunnel junction (MTJ) is a backbone device for spintronics.
Realizing next generation energy efficient MTJs will require operating
mechanisms beyond the standard means of applying magnetic fields or large
electrical currents. Here, we demonstrate a new concept for programmable MTJ
operation via strain control of the magnetic states of CrSBr, a layered
antiferromagnetic semiconductor used as the tunnel barrier. Switching the CrSBr
from antiferromagnetic to ferromagnetic order generates a giant tunneling
magnetoresistance ratio without external magnetic field at temperatures up to ~
140 K. When the static strain is set near the phase transition, applying small
strain pulses leads to active flipping of layer magnetization with controlled
layer number and thus magnetoresistance states. Further, finely adjusting the
static strain to a critical value turns on stochastic switching between
metastable states, with a strain-tunable sigmoidal response curve akin to the
stochastic binary neuron. Our results highlight the potential of
strain-programmable van der Waals MTJs towards spintronic applications, such as
magnetic memory, random number generation, and probabilistic and neuromorphic
computing.
