Exchange bias effects in Heusler alloy Ni2MnAl/Fe bilayers

Ni2MnAl Heusler alloy thin films were epitaxially grown on MgO(1 0 0) single crystal substrates by ultra-high-vacuum magnetron sputtering technique. X-ray diffraction and transmission electron microscopy observation revealed that the structures of all the Ni2MnAl thin films were B2-ordered regardless of the deposition temperature ranging from room temperature to 600 degrees C. The temperature dependence of electrical resistivity showed a kink about 280 K, which was consistent with a reported value of the Neel temperature for antiferromagnetic B2-Ni2MnAl. The magnetization curves of Ni2MnAl/Fe bilayer samples showed a shift caused by the interfacial exchange interaction at 10 K. The maximum value of the exchange bias field H-ex was 55 Oe corresponding to the exchange coupling energy J(k) of 0.03 erg cm(-2).