  Fe-sheathed MgB2 tapes with cheap stearic acid, Mg stearate and Zn stearate
doping were prepared through the in situ powder-in-tube method. It is found
that Jc, Hirr, and Hc2 were significantly enhanced by doping. Compared to the
pure tapes, Jc for all the doped samples was improved by more than an order of
magnitude in a high-field regime. At 4.2 K, the transport Jc reached 2.02x10^4
A/cm^2 at 10 T for the Zn stearate doped tapes and 3.72x10^3 A/cm^2 at 14 T for
the stearic acid doped samples, respectively, equivalent to that of tapes
achieved by nanoscale SiC or carbon doping. The improvement of Jc-H properties
in doped samples can be attributed to the increase of Hc2 resulting from the
incorporation of C atoms into the MgB2 crystal lattice as well as a high
density of flux-pinning centers.
