My lecture notes state that you can distinguish between high spin and low spin complexes by their magnetic properties.
This thought came to me: consider two octahedral crystal fields with a d7 electronic configuration, one in the high spin state and the other in the low spin state. The complex in the high spin state has two unpaired electrons, whereas the complex in the low spin state has 1 unpaired electron. Both complexes are therefore paramagnetic and hence attract magnets. Does the former attract magnets more strongly as it has more unpaired electrons?