  We report the structural and magnetic results of polar {\alpha}-GeTe doped
with Sn and Mn from x = 0.185 to 0.841 and y = 0.02 to 0.086, respectively. The
magnetic results of Ge1-x-y(SnxMny)Te (GSMT) crystals identify Mn-clustering
effect with scaling parameter, R = 0.033 for x ~ 0.2 and y = 0.06. The
excessive Sn ions are assumed to drive the inception of short range
ferromagnetic clusters. For the crystals revealing glassy magnetic behavior,
the irreversibility temperature, Tirr shifts at high dc magnetic field which is
well described by de Almeida-Thouless equation, {\delta}Tirr ~ H{\Phi}/2
yielding {\Phi} values of 1.55 and 1.7 that validates the formation of Mn
clusters. The spin relaxation time, {\tau}0 ~ 10-9 s, activation energy, Ea/kB
~ 5 TF where TF is freeing temperature and Vogel-Fulcher temperature, T0 ~ TF
also signify intracluster interactions. Also, the Mn-hole magnetic exchange
constant, Jpd drops from 0.24 eV for the samples with smaller Sn content of x ~
0.2 to 0.16 eV for Sn rich alloy with x ~ 0.8. Consequently, we present a
magnetic phase diagram for GSMT bulk crystals as a function of Mn(y) ions.
