Influence of B Content on the Magnetostrictive Properties of Single-Crystalline, Poly-Crystalline, and Amorphous Fe-Co-B Alloy Films

Abstract

Fe0.7Co0.3)100-xBx (x = 0-15, at. %) alloy films of 100 nm thickness are prepared on VN(001) single-crystalline underlayers at 600 °C and on VN poly-crystalline underlayers at room temperature (RT). A high substrate temperature of 600 °C is used to promote epitaxial film growth on VN(001) underlayer. Influences of B content on the structural, magnetic, and magnetostrictive properties are investigated. The films formed on VN(001) underlayers involve bcc(001) epitaxial crystalline phase, whereas those formed on VN poly-crystalline underlayers consist of poly-crystalline and/or amorphous phases. Surface roughness of film formed on VN(001) underlayer at 600 °C increases with increasing the B content, whereas flat surfaces are realized for the films formed on VN poly-crystalline underlayers at RT. The surface morphology is influenced by both the substrate temperature and the B content. The films with flat surfaces show good soft magnetic properties. In contrast, rough surface causes an increase in the saturation magnetic field. In the case of films formed on VN(001) single-crystalline underlayer at 600 °C, magnetostriction value of λ100 increases from +200 × 10 -6 to +310 × 10 -6 , as the B content increases from x = 0 to 5. With further increasing the B content, λ100 value decreases due to unsaturation of magnetization at a magnetic field of 1200 Oe which is the maximum value used for measurement. λ111 values are nearly zero (-10 × 10 -6 -+20 × 10 -6 ) for all the investigated B contents. Slight addition of B atoms around 5 at. % is effective in enhancing the λ100 value, while keeping high crystallographic quality, flat surface, and soft magnetic property. On the contrary, the films formed on VN poly-crystalline underlayers at RT show moderately large λ values of about +60 × 10 -6 for all the B contents. The present study shows that control of B content and realization of flat surface are important factors in enhancing the magnetostriction of Fe-Co-B film.

Boron-induced magneto-optical Kerr spectra and dielectric tensors in ferrimagnetic (Mn4N)B antiperovskite thin films

“…This can be attributed to the grain growth compared to that at lower B content, as shown in the AFM images. It is inferred that the surface energy is enhanced as the B content increases, which is in agreement with the case of (FeCo)B systems [45]. Note that the minimum R a for 1.4 at.% is due to the improved fabrication process for further flatness, that is, the film was annealed after the deposition.…”

Compositional dependence of magnetostrictive effect in Ta/CoFe(B)/MgO stacks with perpendicular magnetic anisotropy

“…The ip and op coercive fields (H c ) were obtained from hysteresis loops measured by the magneto-optic-Kerr-effect (MOKE) with the field sweep rate of 1.0 Hz in the longitudinal and polar configuration, respectively. By means of an automated cantileverbeam Lafouda tester at rotating fields around 50 Oe applied along the film surfaces [18], the saturation magnetostriction (λ s ) of CoFe(B) on the underlayer of Ta were characterized with increasing Co composition.…”