  Two-dimensional (2D) van der Waals (vdW) magnetic materials with high
coercivity and high $T_\text{C}$ are desired for spintronics and memory storage
applications. Fe$_3$GeTe$_2$ (F3GT) is one such 2D vdW ferromagnet with a
reasonably high $T_\text{C}$, but with a very low coercive field, $H_\text{c}$
($\lesssim$100~Oe). Some of the common techniques of enhancing $H_\text{c}$ are
by introducing pinning centers, defects, stress, doping, etc. They involve the
risk of undesirable alteration of other important magnetic properties. Here we
propose a very easy, robust, and highly effective method of phase engineering
by altering the sample growth conditions to greatly enhance the intrinsic
coercivity (7-10 times) of the sample, without compromising its fundamental
magnetic properties ($T_\text{C}\simeq$210K). The phase-engineered sample
(F3GT-2) comprises of parent F3GT phase with a small percentage of randomly
embedded clusters of a coplanar FeTe (FT) phase. The FT phase serves as both
mosaic pinning centers between grains of F3GT above its antiferromagnetic
transition temperature ($T_\text{C1}\sim$70~K) and also as anti-phase domains
below $T_\text{C1}$. As a result, the grain boundary disorder and metastable
nature are greatly augmented, leading to highly enhanced coercivity, cluster
spin glass, and meta-magnetic behavior. The enhanced coercivity ($\simeq$1~kOe)
makes F3GT-2 much more useful for memory storage applications and is likely to
elucidate a new route to tune useful magnetic properties. Moreover, this method
is much more convenient than hetero-structure and other cumbersome techniques.
