Graded-index magnonics

• Published in: Физика низких температур
• Date: 2015
• Main Authors: Davies, C.S., Kruglyak, V.V.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2015
• Subjects: К 80-летию уравнения Ландау–Лифшица
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/128079
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Graded-index magnonics / C.S. Davies, V.V. Kruglyak // Физика низких температур. — 2015. — Т. 41, № 10. — С. 976–983. — Бібліогр.: 97 назв. — англ.

The wave solutions of the Landau–Lifshitz equation (spin waves) are characterized by some of the most
 complex and peculiar dispersion relations among all waves. For example, the spin-wave (“magnonic”) dispersion
 can range from the parabolic law (typical for a quantum-mechanical electron) at short wavelengths to the
 nonanalytical linear type (typical for light and acoustic phonons) at long wavelengths. Moreover, the longwavelength
 magnonic dispersion has a gap and is inherently anisotropic, being naturally negative for a range of
 relative orientations between the effective field and the spin-wave wave vector. Nonuniformities in the effective
 field and magnetization configurations enable the guiding and steering of spin waves in a deliberate manner and
 therefore represent landscapes of graded refractive index (graded magnonic index). By analogy to the fields of
 graded-index photonics and transformation optics, the studies of spin waves in graded magnonic landscapes can
 be united under the umbrella of the graded-index magnonics theme and are reviewed here with focus on the challenges
 and opportunities ahead of this exciting research direction.