Magnetostrictive properties of Co-Fe alloy epitaxial thin films with Co-rich composition

Co 75 Fe 25 (at. %) alloy films of 100 nm thickness are prepared on MgO(001) and (110) single-crystal substrates. A Co 75 Fe 25 (001) bcc single-crystal film is epitaxially grown on the MgO(001) substrate, whereas a Co 75 Fe 25 (211) bcc bi-crystalline film is formed on the MgO(110) substrate. The out-of-plane and in-plane lattice spacings of Co 75 Fe 25 films are in agreement with the bulk values within small differences of less than 1%. The out-of-plane and in-plane orientation dispersions are smaller than 2°. These results show that well-defined Co 75 Fe 25 epitaxial films consisting of single bcc phase are successfully obtained on both the MgO(001) and (110) substrates. The in-plane magnetic anisotropies of single- and bi-crystalline films are confirmed to be reflecting the magnetocrystalline anisotropy of Co 75 Fe 25 crystal with the easy and hard axes and the demagnetization field. The magnetostriction coefficients, ( λ 100 , λ 111 ), of single- and bi-crystalline films are determined to be (+60×10 –6 , +150×10 –6 ) and (+55×10 –6 , +185×10 –6 ), respectively. The present study has shown that a Co-Fe alloy with Co-rich composition has positive moderately-large λ 100 and fairly-large λ 111 values.