  Using dc and ac magnetometry, the pressure dependence of the magnetization of
the three-dimensional antiferromagnetic coordination polymer
Mn(N(CN)$_{2}$)$_{2}$ was studied up to 12 kbar and down to 8K. The magnetic
transition temperature, $T_c$, increases dramatically with applied pressure
$(P)$, where a change from $T_c(P=\text{ambient}) = 16.0$ K to
$T_c(P=12.1$~kbar$) = 23.5$ K was observed. In addition, a marked difference in
the magnetic behavior is observed above and below 7.1 kbar. Specifically, for
$P<7.1$ kbar, the differences between the field-cooled and zero-field-cooled
(fc-zfc) magnetizations, the coercive field, and the remanent magnetization
decrease with increasing pressure. However, for $P>7.1$ kbar, the behavior is
inverted. Additionally, for $P>8.6$ kbar, minor hysteresis loops are observed.
All of these effects are evidence of the increase of the superexchange
interaction and the appearance of an enhanced exchange anisotropy with applied
pressure.
