Phase Shift in AC Magnetocaloric Effect Measurements as an Indicator of the Order of Magnetic Phase Transitions

It is shown that the phase shift between an applied weak alternating magnetic field and the magnetocaloric response signal of the magnetic material is drastically sensitive to the order of phase transition. Namely, at the second-order phase transition, the phase shift does not depend on the magnetic field magnitude, while in the first-order phase transition this one depends significantly on the field strength. We have shown that this effect follows from the general critical dynamics theory.