PUBLISHED ; Cited By :1 Export Date: 13 January 2017 ; Narrow-band terahertz emission from coherently excited spin precession in metallic ferrimagnetic Mn3-xGa Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition in the range of 0.20–0.35 THz, making this type of metallic film a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is furthermore shown to be a sensitive probe of magnetic properties of ultra-thin films. ; N.A. acknowledges support through the Ubbo Emmius Program of the University of Groningen. K.R., Y.C.L., D.B., N.T., and J.M.D.C. acknowledge the funding by the SFI through AMBER and Grant No. 13/ERC/12561. D.B. acknowledges funding through IRCSET. O.Y. would like to thank Dr. S. Zhou (HZDR) for the access and assistance to the VSM. R.A.G. acknowledges the financial support from CONICYT PAI/ACADEMIA, under Contract No. 79140033. C.F., O.Y., and A.M.D. acknowledge support by Helmholtz Young Investigator Initiative Grant No. VH-N6-1048