Graded magnetic materials

Abstract

Graded magnetic materials represent a promising new avenue in modern material science from both fundamental and application points of view. Over the course of the last few years, remarkable results have been obtained in (epitaxial) heterostructures based on thin alloy films featuring diverse compositional depth profiles. As a result of the precise tailoring of such profiles, the exchange coupling, and the corresponding effective or local Curie temperatures can be controlled over tens of nm with an excellent precision. This topical review article reports the most recent advances in this emerging research field. Several aspects are covered, but the primary focus lies in the study of compositional gradients being transferred into depth dependent magnetic states in ferromagnets, while also reviewing other experimental attempts to create exchange graded films and materials in general. We account for the remarkable progress achieved in each sample and composition geometry by reporting the recent developments and by discussing the research highlights obtained by several groups. Finally, we conclude the review article with an outlook on future challenges in this field.

Finding order in disorder: Magnetic coupling distributions and competing anisotropies in an amorphous metal alloy

“…Each sample has a well-defined global Curie temperature, where the remanence is reduced to zero, but, nonetheless, we can define a local Curie temperature that can be higher or lower, depending on the local concentration of the magnetic element. [32][33][34] At the global Tc, there may still exist disconnected regions that are magnetically ordered, but they do not exhibit long range ordering in the absence of an external field. These are essentially superparamagnetic regions that are easily polarizable and can mediate exchange coupling and proximity effects over several tens of nanometers.…”

Compositionally graded crystals as a revived approach for new crystal engineering for the exploration of novel functionalities

“…B. J. Kirby and L. Fallarino et al also reported the fabrication of exchange strength modulated ferromagnetic alloy films of Co 1− x Ru x in which the up- and down-graded composition sequence was repeated on a nanometer scale. 43 A recent review by this group 44 would be helpful for more details on magnetic metal alloy NCGCs.…”

Пленка сплава Pd-Fe с большим градиентом магнитной примеси: структурные и магнитные свойства

“…В последние несколько лет в зарубежной литературе, посвященной исследованию магнитных материалов и сплавов, можно встретить термин " Graded Magnetic Materials" или градиентные магнитные материалы (ГММ), это материалы, которые проявляют пространственно-зависящие магнитные свойства (см., например, обзор [1] и ссылки в нем, а также работу [2]). ГММ привлекают внимание исследователей как с фундаментальной, так и с прикладной точек зрения, потому что путем подбора профилей распределения состава по глубине становится возможным контролировать обменное взаимодействие и соответствующие эффективные или локальные температуры Кюри на масштабах нескольких нанометров [1,3,4].…”