  Materials with very low DC magnetic susceptibility have many scientific
applications. To our knowledge however, relatively little research has been
conducted with the goal to produce a totally nonmagnetic material. This phrase
in our case means after spatially averaging over macroscopic volumes, it
possesses an average zero DC magnetic susceptibility. We report measurements of
the DC magnetic susceptibility of three different types of nonmagnetic
materials at room temperature: (I) solutions of paramagnetic salts and
diamagnetic liquids, (II) liquid gallium-indium alloys and (III) pressed powder
mixtures of tungsten and bismuth. The lowest measured magnetic susceptibility
among these candidate materials is in the order of 10^-9 cgs volume
susceptibility units, about two orders of magnitude smaller than distilled
water. In all cases, the measured concentration dependence of the magnetic
susceptibility is consistent with that expected for the weighted sum of the
susceptibilities of the separate components within experimental error. These
results verify the Wiedemann additivity law and thereby realize the ability to
produce materials with small but tunable magnetic susceptibility. For our
particular scientific application, we are also looking for materials with the
largest possible number of neutrons and protons per unit volume. The
gallium-indium alloys fabricated and measured in this work possess to our
knowledge the smallest ratio of volume magnetic susceptibility to nucleon
number density per unit volume for a room temperature liquid, and the
tungsten-bismuth pressed powder mixtures possess to our knowledge the smallest
ratio of volume magnetic susceptibility to nucleon number density per unit
volume for a room temperature solid. This ratio is a figure of merit for a
certain class of precision experiments that search for possible exotic
spin-dependent forces of Nature.
