  MAGIC is a system of two Cherenkov telescopes located in the Canary island of
La Palma. A key part of MAGIC Fundamental Physics program is the search for
indirect signals of Dark Matter (DM) from different sources. In the Milky Way,
DM forms an almost spherically symmetric halo, with a density peaked towards
the center of the Galaxy and decreasing toward the outer region. We search for
DM decay signals from the Galactic Halo, with a special methodology developed
for this work. Our strategy is to compare pairs of observations performed at
different angular distances from the Galactic Center, selected in such a way
that all the diffuse components cancel out, except for those coming from the
DM. In order to keep the systematic uncertainty of this novel background
estimation method down to a minimum, the observation pairs have been acquired
during the same nights and follow exactly the same azimuth and zenith paths. We
collected 20 hours of data during 2018. Using half of them to determine the
systematic uncertainty in the background estimation of our analysis, we obtain
a value of 4.8\% with no dependence on energy. Accounting for this systematic
uncertainty in the likelihood analysis based on the 10 remaining hours of data
collected so far, we present the limit to TeV DM particle with a lifetime of
$10^{26}$ s in the $\mathrm{b\bar{b}}$ decay channel.
