  In this paper, we have found a family of intermetallic compounds YMn12-xFex
(x = 6.6-8.8) showing a bulk form of tunable giant exchange bias effect which
arises from global interactions among ferromagnetic (FM) and antiferromagnetic
(AFM) sublattices but not the interfacial exchange coupling or inhomogeneous
magnetic clusters. A giant exchange bias with a loop shift up to 6.1 kOe has
been observed in YMn4.4Fe7.6 compound with the strongest competing magnetic
interactions. In a narrow temperature range, the exchange bias field shows a
sudden switching off whereas the coercivity shows a sudden switching on with
increasing temperature. This unique feature indicates that the inter-sublattice
exchange coupling is highly homogenous, which can be perfectly interperated by
our theoretical calculations.
