  More-versatile memory is strongly desired for end-users to protect their
information in the information era. In particular, bit-level switchable memory,
from rewritable to read-only function, allows end-users to prevent any
important data from being tampered with. However, no such switchable memory has
been reported. We demonstrated the rewritable function can be converted into a
read-only function by a sufficiently large current pulse in a U-shaped
domain-wall memory composed of an asymmetric Pt/Co/Ru/AlOx heterostructure with
strong Dzyaloshinskii-Moriya interaction. Wafer-scale switchable magnetic
domain-wall memory arrays on 4-inch Si/SiO2 substrate were designed and
fabricated. Furthermore, we confirmed the information can be stored in
rewritable or read-only state at bit-level according to the security-needs of
end-users. Our work not only provides a solution for personal confidential
data, but also paves the way for developing multi-functional spintronic
devices.
