Orbital contribution to perpendicular magnetic anisotropy in Co80Pt20 thin films

Abstract

We have measured x-ray magnetic circular dichroism spectra at the Co and Pt L2,3-edges in Co80Pt20 perpendicular magnetization films, wherein the uniaxial magnetic anisotropy constant, Ku, significantly increases with decreasing film thickness, δ, and reaches 1.7×107 erg/cm3 for δ=3 nm. The anisotropy of the orbital magnetic moment (AOM) was estimated as a function of δ, and the relationship between AOM and Ku is discussed. When the thickness was reduced, the AOM for Pt 5d was nearly constant, whereas a weak increase was observed for Co 3d. Both AOMs are small in contrast to the large Ku, and any proportionality between AOM and Ku was hardly recognized. This result indicates that a large AOM is not always a necessary and sufficient condition for the appearance of perpendicular magnetization.

Microscopic origin of the reduced magnetocrystalline anisotropy with increasing oxide content in Co80Pt20 : oxide thin films

“…Based on the relation m L,60 • increases rapidly with increasing OVF, reaching a value of ∼0.20 µ B /atom at OVF = 0.19, where the orbital moment is nearly isotropic. This high value corresponds to a large orbital-to-spin moment ratio of ∼0.15, comparable to values reported for various CoPt thin films [20,29]. Since m L,0 • is virtually constant, the strongly increasing trend of m L,90 • leads to a distinctly decreasing behaviour of m L with increasing oxide content.…”

“…In this work, we use angle-dependent XMCD to quantify the spin and orbital moments of Co, which represent the main source of magnetization in CoPt : oxide thin films [20]. By studying the dependence of the microscopic magnetic moments on the oxide volume fraction, we have observed an increase in orbital moment normal to the grain-oxide interface with increasing oxide volume fraction, caused by the symmetry breaking at the grain-oxide interface, which plays a dominant role in the K 1 drop.…”

Induced perpendicular magnetization in a Cu layer inserted between Co and Pt layers revealed by x-ray magnetic circular dichroism

“…reported the spin and orbital moment values of Pt as 0.144 and 0.018 μ B , respectively, for the Co/Pt interface8. Both spin and orbital moment values of Pt deduced in our case are half of those estimated for the Co/Pt interface48 because of the suppression of the direct proximity between Co and Pt atoms. The perpendicular components in orbital moments of each element taken at NI were calculated to be 0.15, 0.01, and 0.005 μ B for Co, Cu, and Pt, respectively.…”

“…CoPt alloys such as granular alloys and core-shell particles are candidates for demonstrating PMA through the large spin-orbit interaction of Pt atoms and the spin magnetic moments of Co atoms, which collaborate to enhance the PMA. There are many reports discussing PMA in Co/Pt interfaces, Co-Pt alloys, and granular thin films 3 4 5 6 7 8 , especially using x-ray magnetic circular dichroism (XMCD) to deduce the element-specific spin and orbital magnetic moments. Anisotropy of orbital magnetic moments is expected to play an important role in PMA.…”

Magnetocrystalline anisotropy of magnetic grains in Co80Pt20:oxide thin films probed by x-ray magnetic circular dichroism

“…In this paper, we measured the angle-dependent XMCD hysteresis loops at the Co L 2,3 edges for a series of Co 80 Pt 20 :oxide thin films with variable OVF of ~16.6% to 20.7%. In 3d-5d transition metal alloys, such as CoPt, the net magnetization mainly arises from the Co 3d magnetic moment, while the Pt 5d states carry a small component induced by the 3d-5dhybridization 7 . This means that despite the important role of the hybridization in giving rise to the giant magnetocrystalline anisotropy of the Co-Pt systems 8 …”