We prove optimal energy scaling laws for cubic ferromagnets where the role of magnetostriction is significant. The argument shows the optimality at the level of energy scaling, of the recent highly nontrivial, multi-scale construction known as the zig-zag Landau state reported for Galfenol. It also answers a question raised by Choksi-Kohn-Otto on branched microstructures in Iron. The proof of the lower bound makes use of tools from Fourier analysis, some interpolation inequalities, and a laminate decomposition in Fourier space. This is joint work with Richard D. James and Vivekanand Dabade.