Magnetic Compton scattering is an extension of the previously mentioned technique which involves the magnetisation of a crystal sample hit with high energy, circularly polarised photons. By measuring the scattered photons' energy and reversing the magnetisation of the sample, two different Compton profiles are generated (one for spin up momenta and one for spin down momenta). Taking the difference between these two profiles gives the magnetic Compton profile (MCP), given by J mag ( p z ) – a one-dimensional projection of the electron spin density. J mag ( p z ) = 1 μ μ ∬ ∬ − − ∞ ∞ ∞ ∞ ( n ↑ ↑ ( p ) − − n ↓ ↓ ( p ) ) d p x d p y where μ μ is the number of spin-unpaired electrons in the system, n ↑ ↑ ( p ) and n ↓ ↓ ( p ) are the three-dimensional electron momentum distributions for the majority spin and minority spin electrons respectively.