In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

https://ralphgroup.lassp.cornell.edu/papers/JMMM-320-1190-2008.pdf

Spin transfer torques

New microproducts need the utilization of a diversity of materials and have complicated three-dimensional (3D) microstructures with high aspect ratios. To date, many micromanufacturing processes have been developed but specific class of such processes are applicable for fabrication of functional and true 3D microcomponents/assemblies. The aptitude to process a broad range of materials and the ability to fabricate functional and geometrically complicated 3D microstructures provides the additive manufacturing (AM) processes some profits over traditional methods, such as lithography-based or micromachining approaches investigated widely in the past. In this paper, 3D micro-AM processes have been classified into three main groups, including scalable micro-AM systems, 3D direct writing, and hybrid processes, and the key processes have been reviewed comprehensively. Principle and recent progress of each 3D micro-AM process has been described, and the advantages and disadvantages of each process have been presented.

/pdf/a-review-on-3d-micro-additive-manufacturing-technologies-1kbpeb2xb5.pdf

A review on 3D micro-additive manufacturing technologies

In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.

Integrated optics

http://www2.physics.colostate.edu/groups/WuGroup/publications/MMM_2009_Recent%20advances%20in%20processing%20and%20applications%20of%20microwave%20ferrites.pdf

Recent advances in processing and applications of microwave ferrites

https://arxiv.org/pdf/cond-mat/0310737.pdf

Magnetization reversal by injection and transfer of spin: experiments and theory

Nano-size ferromagnetic dots, wires, and stripes are of great interest for future high speed magnetic sensors and ultrahigh density magnetic storage. High frequency dynamic excitation is one way to investigate the time scale of the magnetization reversal in submicron particles with lateral nanometer dimension. Macroscopic models like the Landau–Lifshitz (LL) model are often used to describe the switching process. However, these models do not take into account the nonuniformity of the magnetization structure. In this article dynamic micromagnetic calculations are used in determining the high frequency susceptibility of a 1 μm×50 nm×5 nm Permalloy stripe. The studied structure exhibits two resonance modes. The higher, primary peak is around 10 GHz and can be identified with the uniform resonance mode predicted by the macroscopic LL model. The low frequency peak is attributed to the splay of the magnetization distribution near the end of the stripe.

Micromagnetic Calculation of the High Frequency Dynamics of Nano-Size Rectangular Ferromagnetic Stripes

The ferromagnetic resonance (FMR) spectra in magnetic films with a nonuniform magnetization configuration are known to exhibit multiple absorption peaks. In this paper, the case of ferromagnetic films supporting a weak stripe domain structure is addressed. A two-dimensional dynamic micromagnetic model is used to investigate the high-frequency response of such a magnetic structure. In a first step, the zero-field susceptibility spectra are computed. The existence of numerous resonances resulting from the excitation of surface and volume modes is predicted. The main features of spectra (number of resonances, resonance frequencies, intensities, and linewidths) strongly depend on the equilibrium spin configuration and on the rf exciting field orientation. In a second step, the susceptibility spectra in the presence of an in-plane static magnetic field applied along the stripe direction are studied in detail. The dispersion relation, frequency versus in-plane magnetic field, is computed for each magnetic excitation. These dispersion curves reveal possible mode couplings and interchange of mode characters with increasing magnetic field. The theoretical in-plane FMR spectra are then deduced from the frequency and magnetic field dependence of the dynamic susceptibility. These theoretical results are discussed in light of available experimental FMR data obtained on thin ferromagnetic films with a moderate perpendicular anisotropy.

Ferromagnetic resonance spectra in a weak stripe domain structure

On three fluorides CeF3, NdF3, and PrF3 accurate susceptibilities measurements are reported from 2 up to 300 K under a magnetic field applied along the c axis. On the same samples, the optical Faraday rotation has been investigated in the temperature range 8–300 K at 0.6328 μm wavelength in a magnetic field up to 20 kOe. The reciprocal susceptibilities χ−1(T) follow a Curie Weiss law for T>100 K; the observed values of the paramagnetic Curie temperature are − 56 K (PrF3), − 114 K (CeF3), and − 26 K (NdF3). For T 77 K. (V and χ are expressed in deg cm−1 Oe−1 and in μB mol−1 Oe−1, respectively.) On one hand for NdF3 and PrF3, it ...

H. Le Gall

Papers

Magnetization reversal by injection and transfer of spin: experiments and theory

Micromagnetic Calculation of the High Frequency Dynamics of Nano-Size Rectangular Ferromagnetic Stripes

Ferromagnetic resonance spectra in a weak stripe domain structure

Magnetic susceptibility and Verdet constant in rare earth trifluorides

Constructal approach and multi-scale components