Exchange coupling in single-crystalline spinel-structure (Mn,Zn)Fe2O4/CoFe2O4 bilayers

We have observed strong exchange coupling between single-crystalline spinel-structure ferrite thin films of CoFe2O4 and magnetically soft (Mn,Zn)Fe2O4 at room temperature. The exchange coupling constant of the interface, A(int) which is estimated from exchange-biased (Mn,Zn)Fe2O4 loops is comparable to estimated exchange coupling constants within each individual layer, A(MZF) and A(CF). This result contrasts with exchange coupling in polycrystalline Ni0.8Fe0.2/Mn0.5Fe0.5 and Ni0.8Fe0.19/Ni0.53Mn0.47 bilayers where A(int) is at best two orders of magnitude smaller than estimates of A(NiFe).