  We present a general finite element linearized Landau-Lifshitz-Gilbert
equation (LLGE) solver for magnetic systems under weak time-harmonic excitation
field. The linearized LLGE is obtained by assuming a small deviation around the
equilibrium state of the magnetic system. Inserting such expansion into LLGE
and keeping only first order terms gives the linearized LLGE, which gives a
frequency domain solution for the complex magnetization amplitudes under an
external time-harmonic applied field of a given frequency. We solve the linear
system with an iterative solver using generalized minimal residual method. We
construct a preconditioner matrix to effectively solve the linear system. The
validity, effectiveness, speed, and scalability of the linear solver are
demonstrated via numerical examples.
