Abstract
The present work investigated interlayer couplings of [Co(20 Å)/Pt(30 Å)]5, [Co(4 Å)/Pt(7 Å)]30, and [Co(4 Å)/Pt(9 Å)]30multilayers with strong perpendicular magnetic anisotropy (PMA). Brillouin light scattering measurements were utilized to obtain spin waves of these samples with in-plane external magnetic fields. Interlayer couplings were found to be very sensitive to Pt thickness change from 7 Å to 9 Å, which implies that Pt atoms were more difficult to be polarized to provide interlayer coupling between Co layers than in the perpendicular external magnetic field situation. When Pt layer is 30 Å, the observed single spin wave can confirm the disappearance of interlayer coupling even when Co layer thickness is 20 Å.
Highlights
Since the first observation of spin waves in 1946 by Griffiths [1], with wide applications of laser in light scattering experiments and the invention of multipass Febry Perot interferometer by Sandercock in 1970 [2], Brillouin scattering became an important tool in the field of magnetism to detect different kinds of magnetic excitations in various systems, including bulk materials, thin films, and nanostructures
We believe that the observed spin wave energies increase linearly with the external magnetic fields H rather than in the form of square root of H, which is a typical behavior of spin waves whose wave vector q is parallel rather than perpendicular to the magnetization M
There are two weak peaks around 4 GHz and 9 GHz at high magnetic fields of 7.0 KOe and 8.0 KOe, which show no changes with magnetic fields; they were confirmed as phonons from Brillouin scattering measurements without magnetic fields
Summary
Since the first observation of spin waves in 1946 by Griffiths [1], with wide applications of laser in light scattering experiments and the invention of multipass Febry Perot interferometer by Sandercock in 1970 [2], Brillouin scattering became an important tool in the field of magnetism to detect different kinds of magnetic excitations in various systems, including bulk materials, thin films, and nanostructures. Many theoretical and experimental works were devoted to this field in understanding its magnetic behaviors especially for the perpendicular magnetic anisotropy thin films [3–7] through different approaches like neutron scattering, ferromagnetic resonance, magneto-optical Kerr microscopy, and Brillouin scattering. [Co(4 A )/Pt(7 A )]30, and [Co(4 A )/Pt(9 A )]30 use Brillouin scattering to detect spin waves, from which magnetic coupling behaviors can be deduced and compared with experiments with magnetic fields perpendicular to the sample surface. Due to the weak in-plane magnetic anisotropy, three strong PMA samples will have different spin waves when Co and Pt thickness changed providing another approach to understand magnetic coupling of this system
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