Opposite-axis quadratic anisotropy of a vector order parameter ($f=\frac{1}{2}t|m{|}^2+u|m{|}^4+\frac{1}{2}r(m_1^2-m_2^2)$)

For $u>0$ and $t>0$, minimizing a uniform field gives zero magnetization when $|r|\le t$. For $r<-t$ only component 1 orders, with $m_1^2=-(t+r)/(4u)$; for $r>t$ only component 2 orders, with $m_2^2=(r-t)/(4u)$. Both transition lines are continuous. The positive-$t$ disordered wedge separates the two easy-axis phases.