http://mcs.open.ac.uk/au73/papers/JMMM200_248.pdf

Spin polarized tunneling in ferromagnetic junctions

A comprehensive review and state of the art in the field of surface, interface, and thin-film magnetism is presented. New growth techniques which produce atomically engineered novel materials, special characterization techniques to measure magnetic properties of low-dimensional systems, and computational advances which allow large complex calculations have together stimulated the current activity in this field and opened new opportunities for research. The current status and issues in the area of material growth techniques and physical properties, characterization methods, and theoretical methods and ideas are reviewed. A fundamental understanding of surface, interface, and thin-film magnetism is of importance to many applications in magnetics technology, which is also surveyed. Questions of fundamental and technological interest that offer opportunities for exciting future research are identified.

/pdf/surface-interface-and-thin-film-magnetism-1txr0q0vir.pdf

Surface, interface, and thin-film magnetism

▪ Abstract Based on the spin conservation in electron tunneling across an insulator (I) and the spin polarization of conduction electrons in ferromagnets (FM) established by Meservey and Tedrow, Julliere put forward a quantitative model (1975) showing that tunneling in FM-I-FM junctions should lead to a large junction magnetoresistance (JMR). This conjecture was realized with repeatable results only in 1995, and since then JMR values >30% have been achieved at room temperature. This phenomenon has tremendous potential for applications as nonvolatile magnetic memory elements, read heads, and picotesla field sensors. We review the experimental results and the current theoretical understanding of FM-I-FM tunneling and its dependence on bias, temperature, and barrier characteristics. The influence of inelastic tunneling processes and material properties on the JMR is extensively discussed. Early theories are reviewed and their relationship to the linear response theory is presented. Future directions, both fr...

Spin-tunneling in ferromagnetic junctions

Cobalt-based full-Heusler compounds with composition Co2M'Z (where M' is a transition metal and Z is a main group element) are attracting attention due to their predicted half-metallic behaviour, a greatly desired property for spin-dependent electron transport devices. Knowledge of the basic magnetic properties of these materials, in particular in the form of thin films, is required both to fully exploit these promising materials and to understand their underlying electronic structure and establish structure–property relationships. In this topical review, we present a survey of the magnetic anisotropy, exchange and damping of Co2M'Z compounds. These properties are directly related to spin–spin and spin–orbit interactions.

/pdf/magnetic-anisotropy-exchange-and-damping-in-cobalt-based-5dw51r0qpc.pdf

Magnetic anisotropy, exchange and damping in cobalt-based full-Heusler compounds: an experimental review

The development of surface science and specifically of spin-polarized electron spectroscopy has been the driving force for a new era of surface and 2D magnetism. Classical primary magnetic quantities such as the temperature dependence of the spontaneous magnetization, the Curie point, the magnetic anisotropies, the variation of the quantum mechanical exchange interaction at clean or modified surfaces, and special surface-induced magnetic structures can now be determined with spin-polarized electron spectroscopies. But a variety of new fields are also appearing, for instance ultrafast time-resolved magnetometry employing laser-induced photoemission of spin-polarized electrons, and imaging of magnetic domains with unprecedented spatial resolution via spin-polarized cascade electrons. Furthermore, by analysing the spin of the photoemitted electrons or by observing the Bremsstrahlung emitted when a spin-polarized electron beam strikes the surface, the majority- and minority-spin electron states in ferromagnets can be investigated separately. Three types of spin-split electron state appear at the surface of a ferromagnet: the bulk magnetic bands, the surface states of Schottky type, and the image potential surface states. With ultrathin ferromagnetic films, magnetometry employing the measurement of the spin polarization of low-energy cascade electrons produces magnificent images of the magnetic domains and reveals the conditions for their occurrence. The dramatic response of the spontaneous magnetization to external disturbances such as an applied magnetic field or an exchange field transferred from a substrate is also obtained. The critical phenomena observed in surface and 2D magnetism fit well into the framework set by the theory many years ago, while the theoretically predicted exotic 2D ferromagnetism in elements that do not exhibit magnetism in 3D has not yet been verified beyond doubt.

http://iopscience.iop.org/article/10.1088/0953-8984/4/44/004/pdf

S. B. Ahmad

Papers

Quasi-two-dimensional behavior of the surface magnetization in a ferromagnet with softened surface exchange