Texture formation in FePt thin films via thermal stress management

Abstract

The transformation variant of the fcc to fct transformation in FePt thin films was tailored by controlling the stresses in the thin films, thereby allowing selection of in- or out-of-plane c-axis orientation. FePt thin films were deposited at ambient temperature on several substrates with differing coefficients of thermal expansion relative to the FePt, which generated thermal stresses during the ordering heat treatment. X-ray diffraction analysis revealed preferential out-of-plane c-axis orientation for FePt films deposited on substrates with a similar coefficients of thermal expansion, and random orientation for FePt films deposited on substrates with a very low coefficient of thermal expansion, which is consistent with theoretical analysis when considering residual stresses.

Improvement in surface conditions of electroplated Fe-Pt thick-film magnets

“…2, the films plated on the Ta substrate and the Ti ones have large variations in R a , the tendency of the roughness was clearly divided into two types based on the CTE of the Fe-Pt alloy. 14 This result implies that a substrate with slight higher CTE value compared with the value for the Fe-Pt alloy is preferable, and we found that the Cu plate is a hopeful substrate to fabricate the Fe-Pt thick-film magnets with good surface conditions from Figs. 1-2.…”

High-energy product exchange-spring FePt/Fe cluster nanocomposite permanent magnets

“…FePt thin fi lms deposited on Si displayed random crystallographic orientation after heat treatment (Fig. 2) [24].…”

Effects of Ru and Ag cap layers on microstructure and magnetic properties of FePt ultrathin films

“…For the Ag capped FePt film, the in-plane tension thermal stress, originating from the Ag cap layer, would force the FePt thin film in-plane unit cell expansion, which would relieve the externally applied stress, resulting in (001) orientation in the FePt films. Additionally, considering that the thermal stress originates from the SiO2 substrates of −1.34 GPa and the intrinsic residual tensile stress in sputtering thin metal films of 1.2 to 1.5 GPa [21,22], the stress originating from the substrates will be negligible. Thus, the total thermal stress is equal to that originating from the cap layer.…”