  Magnetars are a kind of pulsars powered mainly by superhigh magnetic fields.
They are popular sources with many unsolved issues in themselves, but also
linked to various high energy phenomena, such as QPOs, giant flares, fast radio
bursts and super-luminous supernovae. In this work, we first review our recent
works on the dissipation of toroidal magnetic fields in magnetars and
rotationally powered pulsars, then review the spin-down evolution of young and
strongly magnetized pulsars, especially of magnetars. We present an interesting
and important relation between the magnetization parameter, and magnetic field
in the magnetar crust. Finally, we introduce our two works in progress: to
explain the magnetar "anti-gltich" events in the thermal plastic flow model and
to revisit the expression of braking index $n$, which is independent of the
second derivative of spin frequency of a pulsar and give some proposals for our
future work.
