statistical mechanics - Are the first order phase transitions always associated with a latent heat?

Is the first order ferromagnetic transition below the critical temperature associated with latent heat?

For example, the transition of ferromagnetic configuration with all its spins aligned up to a ferromagnetic configuration with all its spins aligned down at $T=T_FIs this also associated with latent heat?

If yes, how do we calculate it? $Q=T_F\Delta S$, but I think, $\Delta S=0$ because both up-aligned and down-aligned configurations have same entropy. I'm not quite sure that $\Delta S=0$ because if $\Delta S=0$ how can it be discontinuous? But for this transition to be first order, entropy should be discontinuous according to the Ehrenfest criterion.