Fortran Iterative Solver Library

I wrote code that solves large PDE systems using some sampling techniques, which basically involve solving large, sparse Ax = b systems many times at each time step.

I am currently using the PARDISO solver (from the Intel MKL library) which is a direct LU factorization of A to solve the system. I would like to compare this method using iterative solvers (which using preconditioners could work better as I could use the same preconditioner at many time steps if my Jacobi matrix doesn't change too much).

My question is, what library do you suggest for sparse iterative solvers in fortran? I found one (SLATEC) that was written in 1993, so I am wondering if there is something more perfect that was written more recently?

Thank:)