Solution
= Solution
Put $B=\xi\tan(\phi+\alpha t)$. Matching the constant and $\tan^2$ coefficients in the <Riccati equation> requires
$$
\xi\alpha=-\frac{i}{2\hbar},
\qquad
\xi\alpha=-2i\hbar\xi^2.
$$
One convenient choice is therefore
$$
\boxed{\xi=\frac1{2\hbar},
\qquad \alpha=-i},
$$
so
$$
\boxed{B(t)=\frac1{2\hbar}\tan(\phi-it)}.
$$