A diagram is derived that visualizes the interplay of macroscopic thermal, mechanical, and magnetic effects in a diamagnetic crystal. The derivation is based on a Taylor expansion of a thermodynamic potential and on a theorem on the transformation behaviour of property tensors under time inversion. The interaction diagram provides a quick answer to the experimenter on the question of which linear and quadratic physical effects are possible in the given physical situation and how the measurement of an effect under study might be influenced by cross-effects.