  The magnetic polarisability is a fundamental property of hadrons, which
provides insight into their structure in the low-energy regime. The pion
magnetic polarisability is calculated using lattice QCD in the presence of
background magnetic fields. The results presented are facilitated by the
introduction of a new magnetic-field dependent quark-propagator eigenmode
projector and the use of the background-field corrected clover fermion action.
The magnetic polarisabilities are calculated in a relativistic formalism, and
the excellent signal-to-noise property of pion correlation functions
facilitates precise values.
