Computer studies are made illustrating the similarities of the interesting change of sign in the magnetocaloric effect between the vortex lattice in superconductors and a system of interacting magnons and phonons in ferromagnetic materials. This change happens in the superconducting system when the external magnetic field approaches a critical value, while the critical point in the ferromagnetic system is where the external magnetic field turns the direction of magnetization from the easy to the hard direction. The usefulness for the study of high-temperature superconductors is suggested.