High temperature magnetic properties of Fe81−xCoxGa19/Si(100) films

Abstract

Fe81−xCoxGa19 (with x ranging from 0 to 19 at.% Co) films with thicknesses of about 110 nm were deposited on Si(100) substrates by the dc magnetron sputtering method. The structures of these films at room temperature (RT) were analyzed by x-ray diffraction. Magnetic hysteresis loops of each film were measured from room temperature (RT) to 800 °C, and their saturation magnetization (4πMS) and coercivity (HC) were plotted as a function of temperature (T). Saturation magnetostriction (λS) at RT was also measured. The substitution of Co for Fe would give rise to increases in HC and λS. In terms of high temperature magnetic properties, (A) we find that for each film, there is one low-temperature-phase Curie point (TC1) and one high-temperature-phase Curie point (TC2); (B) based on the temperature dependence of 4πMS, we calculated the reduced hyperbolic Bessel function I∧5/2(T); from the relationship λS(T)=I∧5/2(T)×λS(RT), we can compare the performances of λS(T) at higher temperatures; and (C) HC decreases slightly as T increases initially, but it reaches a maximum when either TC1 or TC2 is approached. It is concluded that the Fe62Co19Ga19 film has the optimal high-temperature magnetic properties, including a larger λS(T), higher TC1, and moderate HC(T).