Magnetic and structural properties of (CoxFe100−x)50Pt50 alloy thin films

Abstract

A study of magnetic and structural properties of (CoxFe100−x)50 (0≦x≦100) alloy thin films as functions of composition and substrate deposition-temperature Ts is carried out. The intrinsic perpendicular magnetic anisotropy Ku starts to increase with deposition temperature Ts for all the films (0≦x≦100) at about TS=250–300 °C, and then becomes nearly constant. The maximum values of Ku at room temperature thus obtained are 6×107, 4×107, and 2×107 erg/cc for Fe50Pt50, (Co43Fe57)50Pt50 and Co50Pt50, respectively. Also, the Ku of Fe50Pt50 films increases with the order parameter (S), being closely related with the tetragonality c/a. These results indicate that the evolution of Ku is due to the occurrence of the ordered fct phase.

Curie temperatures of annealed FePt nanoparticle systems

“…The Curie temperatures of the L1 0 FePt phase are strongly composition dependent and are higher than that of Fe 3 Pt phase. The abnormal dependence of M s at room temperature on x is caused by the low T C of Fe 3 Pt phase with x = 75-79. It was also found that there is a big difference in T C when measured through the heating and cooling thermomagnetic curves of the Fe-Pt alloys with x = 78-90.…”

“…3,4 Near x = 75 large volume instability ͑Invar effect͒ is observed in the L1 2 Fe 3 Pt phase ͑␥ 1 ͒. 5,6 The most recent interests in FePt nanostructured materials have been focused on the ferromagnetic L1 0 FePt phase ͑␥ 2 ͒ because of their potential applications in ultrahigh-density magnetic recording 7,8 and advanced permanent magnets 9,10 due to its very high uniaxial magnetocrystalline anisotropy and high Curie temperatures.…”

Order-Disorder Transformation in L1<SUB>0</SUB>-FePd Nanoparticles Studied by Electron Diffraction

“…Actually, a correlation has been indicated between the long-range order (LRO) parameter and the magnetocrystalline anisotropy energy. 3,4) Hence the LRO parameter is a key factor when the hard magnetic properties of these L1 0 ordered nanoparticles are discussed. As for the small isolated alloy nanoparticles with the ordered phase, particle size dependence of the order-disorder transformation temperature has been indicated and the stabilization of the high-temperature disorder phase due to downsizing has been reported in experimental results on several alloy systems.…”

Magnetism of FePt Surface Alloys

“…STM images with atomically resolved chemical contrast are presented and the system's magnetic properties are analyzed by x-ray magnetic circular dichroism (XMCD). We show that depending on the specific lateral coordination of Fe the magnetism of these surface alloys (SA) can exhibit large out-of-plane magnetic anisotropy, comparable to that of high-anisotropy bulklike FePt alloy films (10-100 nm thickness) [4][5][6], and noncollinear magnetism due to DM interactions. While in bulk FePt large anisotropies are due to noncubic 3D stacking of Fe and Pt layers [7,8], we find a substantially different mechanism for SAs.…”