  Comprehensive magnetic-field-temperature ($H$-$T$) phase diagram of solid
oxygen including the $\theta$ phase is discussed in the context of the
ultrahigh-field measurement and the magnetocaloric effect (MCE) measurement.
The problems originating from the short duration of the pulse field,
non-equilibrium condition and MCEs, are pointed out and dealt with. The
obtained phase diagram manifests the entropy relation between the phases as
$S_\theta \sim S_\alpha<S_\beta<<S_\gamma$.
