A constant current I is flowing through a circular coil placed in uniform magnetic field $\overrightarrow{B}$ as shown. Then

Torque acting on the loop is $\overrightarrow{\mathrm{\tau }}=\overrightarrow{ \mathrm{M} }\times \overrightarrow{\mathrm{B}}=\mathrm{MB}\sin \mathrm{\theta }$

where $\theta$ = angle between M and B

In the figure shown, $\theta ={90}^0$ because B is in plane of loop.

Or  $\tau =MB=$ maximum torque.
Since, torque is acting on the loop, so loop is not in equilibrium.