- steel needle
- iron rods
- water vial? (since diamag it should reduce the field- bh curve should get shorter)
theory: http://vlab.amrita.edu/?sub=1&brch=282&sim=1507&cnt=1
some other info: https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/Permeability.htm