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

Co75Fe25 (at. %) alloy films of 100 nm thickness are prepared on MgO(001) and (110) single-crystal substrates. A Co75Fe25(001)bcc single-crystal film is epitaxially grown on the MgO(001) substrate, whereas a Co75Fe25(211)bcc bi-crystalline film is formed on the MgO(110) substrate. The out-of-plane and in-plane lattice spacings of Co75Fe25 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 Co75Fe25 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 Co75Fe25 crystal with the easy <111> and hard <100> axes and the demagnetization field. The magnetostriction coefficients, (λ100, λ111), 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 λ100 and fairly-large λ111 values.