Most fMRI studies are done using MRI scanners with a field strength of either 1.5 Teslaor, most commonly nowadays, 3.0 Tesla. However, a few especially forward-thinking, by which I mean wealthy, research centres have started investing in 7 Tesla scanners.
Metzger CD, Eckert U, Steiner J, Sartorius A, Buchmann JE, Stadler J, Tempelmann C, Speck O, Bogerts B, Abler B, & Walter M (2010). High field FMRI reveals thalamocortical integration of segregated cognitive and emotional processing in mediodorsal and intralaminar thalamic nuclei. Frontiers in neuroanatomy, 4 PMID: 21088699