The stellar initial mass function (IMF) has a great importance in astrophysics as it is vital for many studies but its behavior is still under discussion, specially in the low mass domain. We present the photometric determination of the system IMF of the 25 Orionis stellar group (25 Ori) from the planetary mass domain to the intermediate-mass regime. Working with optical and near-infrared photometry from DECam and the CIDA Deep Survey of Orion, as well as public data from Hipparcos, UCAC4,

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... and 2MASS, we selected more than 1500 photometric member candidates of 25 Ori according to their positions in color-magnitude and color-color diagrams. This sample has an $I_c$ range from 5.1 to 24.9 mag and covers a field of view of 2.2$^\circ$ in diameter encompassing the 25 Ori overdensity. We worked with a control field at the same galactic latitude of 25 Ori to estimate the contamination in the sample by field stars and extragalactic sources. To estimate the masses of the candidates we used the $M_{I_c}$-mass relations from the stellar models by Baraffe et al. (2015) and Marigo et al. (2017), resulting in a mass range from 12.9 $M_\odot$ down to 9 $M_{Jup}$. We estimated the uncertainties in the derived IMF due to the distances and visual extinctions generated for the member candidates without Gaia DR2 parallaxes or reported extinctions. We fitted a segmented power law, a log-normal and a tapered power law functions to the resulting IMF to compare their parameters with those in other star forming regions. Finally, we present the progress in the follow-up spectroscopy to assign the membership of the candidates in order to determine the IMF with a statistically complete sample of confirmed members. So far, this spectroscopic survey is $\sim$85\% complete using data from GTC/Osiris (Downes et al. 2015), MMT/Hectospec, SDSS-IV/APOGEE-2, SDSS-III/BOSS (Suárez et al. 2017) and OAN-SPM/Echelle.