Universal field dependence of magnetic resonance near zero frequency

Magnetic resonance is a widely established phenomenon that probes magnetic properties such as damping and anisotropy. Even though the typical frequency of magnet ranges from gigahertz to terahertz, experiments also report near zero in large class magnets. Here we revisit this by analyzing symmetry system find $\ensuremath{\omega}$ follows universal power law $\ensuremath{\omega}\ensuremath{\propto}|H\ensuremath{-}{H}_{c}{|}^{p}$, where ${H}_{c}$ critical field at which zero. When preserves rotational around external $H, p=1$. Otherwise, $p=1/2$. The magnon excitations are gapped above ${H}_{c}$, gapless again below ${H}_{c}$. often accompanied reorientation transition magnetization. For case $p=1/2$, described Landau theory for second-order phase transitions. We further show spin current driven thermal gradient spin-orbit effects can be significantly enhanced when close zero, measured electrically converting into electric signals. This may provide an experimentally accessible way characterize field. Our findings unified understanding magnetization dynamics may, furthermore, inspire study transport