  According to Heisenberg ferrmagnetism stems from the Pauli magic mediating
between Coulomb interaction and electrons' spins. The primary aim of the paper
is to turn the magic into an algebra by setting a precise bound to the degree a
given electron density can affect spins. An application of the resulting
spin-orbital Pauli constraints to Fe, Co, and Ni provides a new insight into
the origin of magnetic moments in this archetypical ferromagnets.
