the BEC state can be studied via thermodynamic properties such as magnetization, temperature and specific heat, which are measured when the phase boundary is crossed by sweeping the field or the temperature, as indicated by the arrows.](figure2.eps){width="7cm"}

Since according to (1) $T_{BEC}$ is proportional to $\rho^{2/3}/m$, we would like to maximize $\rho$ to observe the BEC at easily accessible temperatures. However, that equation assumes that the bosons are free particles and is therefore only valid in the limit of low density. We can overcome this problem by considering that $T_{BEC}$ is also dependent on the boson mass $m$. By minimizing $m$, we can observe the BEC at relatively high temperatures without sacrificing the condition of low boson density. In quantum magnets, the boson mass is sufficiently small, so that the BEC can be realized at temperatures of a few Kelvin, in contrast to cold atoms, in which temperatures in the nano-Kelvin range are needed to observe the BEC in magnetic optical traps [@19; @21].

III. MAGNETIC PROPERTIES OF DTN-BEC
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In addition to the properties of NiCl$_{2}$-4SC(NH$_{2}$)$_{2}$, one needs well-prepared samples for studies under laboratory conditions. Single crystals of dichloro-$tetrakis$thiourea-nickel (DTN) were grown by dissolving a large excess of nickel 