  We have performed a search for planetary-mass brown dwarfs in the Chamaeleon
I star-forming region using proper motions and photometry measured from optical
and infrared images from the Spitzer Space Telescope, the Hubble Space
Telescope, and ground-based facilities. Through near-infrared spectroscopy at
Gemini Observatory, we have confirmed six of the candidates as new late-type
members of Chamaeleon I >M7.75. One of these objects, Cha J11110675-7636030,
has the faintest extinction-corrected M_K among known members, which
corresponds to a mass of 3-6 M_Jup according to evolutionary models. That
object and two other new members have redder mid-IR colors than young
photospheres at <M9.5, which may indicate the presence of disks. However, since
those objects may be later than M9.5 and the mid-IR colors of young
photospheres are ill-defined at those types, we cannot determine conclusively
whether color excesses from disks are present. If Cha J11110675-7636030 does
have a disk, it would be a contender for the least-massive known brown dwarf
with a disk. Since the new brown dwarfs that we have found extend below our
completeness limit of 6-10 M_Jup, deeper observations are needed to measure the
minimum mass of the initial mass function in Chamaeleon I.
