In this case, it will be shown that ∇ ∇ 2 ( B x 2 + B y 2 + B z 2 ) ≥ ≥ 0 , which, combined with the constant k, shows that paramagnetic materials can have energy maxima but not energy minima and diamagnetic materials can have energy minima but not energy maxima. That is, paramagnetic materials can be unstable in all directions but not stable in all directions and diamagnetic materials can be stable in all directions but not unstable in all directions. Of course, both materials can have saddle points.