Structural and antiferromagnetic characterization of noncollinear D0₁₉ Mn₃Ge polycrystalline film

Distorted Heusler compound of D0₁₉ Mn₃Ge polycrystalline films were studied in terms of their crystalline structures and antiferromagnetic behavior by varying annealing temperature and Mn-Ge composition. Although low temperature growth for 30 nm Mn₃Ge showed no diffraction peaks in X-ray diffraction patterns, high temperature growth over 773 K with Mn-rich composition is found to promote the (0001) orientation of D0₁₉ Mn₃Ge which resulted in the emergence of an exchange bias effect in Co_0.6Fe_0.4 ferromagnetic layer at 120 K. The exchange bias field of 12 Oe in Mn_3.16Ge film grown at 773 K were improved to 61 Oe by enriching Mn composition to Mn_3.97Ge. The average blocking temperature was measured to be at 150 K which is not as high as its reported Néel temperature of 390 K in the bulk state, however, further improvements are expected by doping additional transition elements.