The exotic properties of magnetic materials provide multiple avenues for research as well as the possibility for energy-efficient, faster and cheaper technologies. Especially, earlier few decades had been crucial for the advancement of memory devices in-terms of size, speed, price and availability. Material science scientific community has been dedicated for developing next generation memory devices. The presence of a strong perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) in magnetic materials serve as building blocks for the formation of skyrmions which are promising candidates for next generation memory devices. This dissertation discusses the fundamentals of Dzyaloshinskii-Moriya interaction (DMI) which is responsible for the formation of skyrmions in magnetic multilayers. Especially this dissertation discusses the First Principle calculation technique and micromagnetic simulations to estimate the magnitude and sign of DMI and estimation of higher-order perpendicular anisotropy in ferromagnetic multilayers.In the first study presented in this dissertation, the basis of DMI, spin spirals and penalty energy parameters are discussed and the magnitude and strength of DMI vector in Pt/Co multilayers is estimated and related with proximity effect. In the second study presented, the origin of higher-order contribution of perpendicular magnetic anisotropy (PMA) are studied in ferromagnetic bilayers using micromagnetic simulations. These simulations showed that spatial inhomogeneities of the first-order perpendicular anisotropy may be the origin of higher-order anisotropies in magnetic multilayers.

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Nanomagnetic Materials: Fabrication, Characterization and Application explores recent studies of conventional nanomagnetic materials in spintronics, data storage, magnetic sensors and biomedical applications. In addition, the book also reviews novel magnetic characteristics induced in two-dimensional materials, diamonds, and those induced by the artificial formation of lattice defect and heterojunction as novel nanomagnetic materials. Nanomagnetic materials are usually based on d- and f-electron systems. They are an important solution to the demand for higher density of information storage, arising from the emergence of novel technologies required for non-volatile memory systems. Advances in the understanding of magnetization dynamics and in the characteristics of nanoparticles or surface of nanomagnetic materials is resulting in greater expansion of applications of nanomagnetic materials, including in biotechnology, sensor devices, energy harvesting, and power generating systems. This book provides a cogent overview of the latest research on novel nanomagnetic materials, including spintronic nanomagnets, molecular nanomagnets, self-assembling magnetic nanomaterials, nanoparticles, multifunctional materials, and heterojunction-induced novel magnetism. - Explains manufacturing principles and process for nanomagnetic materials - Discusses physical and chemical properties and potential industrial applications, such as magnetic data storage, sensors, oscillator, permanent magnets, power generations, and biomedical applications - Assesses the major challenges of using magnetic nanomaterials on a broad scale

Magnetic skyrmions are particle-like objects described by localized solutions of non-linear partial differential equations. Up until a few decades ago, it was believed that magnetic skyrmions only existed in condensed matter as short-term excitations that would quickly collapse into linear singularities. The contrary was proven theoretically in 1989 and evidentially in 2009. It is now known that skyrmions can exist as long-living metastable configurations in low-symmetry condensed matter systems with broken mirror symmetry, increasing the potential applications possible. Magnetic Skyrmions and their Applications delves into the fundamental principles and most recent research and developments surrounding these unique magnetic particles. Despite achievements in the synthesis of systems stabilizing chiral magnetic skyrmions and the variety of experimental investigations and numerical calculations, there have not been many summaries of the fundamental physical principles governing magnetic skyrmions or integrating those concepts with methods of detection, characterization and potential applications. Magnetic Skyrmions and their Applications delivers a coherent, state-of-the-art discussion on the current knowledge and potential applications of magnetic skyrmions in magnetic materials and device applications. First the book reviews key concepts such as topology, magnetism and materials for magnetic skyrmions. Then, charactization methods, physical mechanisms, and emerging applications are discussed. - Covers background knowledge and details the basic principles of magnetic skyrmions, including materials, characterization, statics and dynamics - Reviews materials for skyrmion stabilization including bulk materials and interface-dominated multilayer materials - Describes both well-known and unconventional applications of magnetic skyrmions, such as memristors and reservoir computing

This book focuses on an increasingly important area of materials science and technology, namely, the fabrication and properties of artificial materials where slabs of magnetized materials are sandwiched between slabs of nonmagnetized materials. It includes reviews by experts on the theory and descriptions of the various experimental techniques such as those using nuclear or electron spin probes, as well as optical, X-ray or neutron probes. It also reviews potential applications such as the giant magnetoresistance, and one specialized preparation technique, the electrodeposition. The various chapters are tutorial in nature, making the subject accessible to nonspecialists, as well as useful to researchers in the field.

Magnetic nanowires and microwires are key tools in the development ofenhanced devices for information technology (memory and data processing) andsensing. Offering the combined characteristics of high density, high speed, andnon-volatility, they facilitate reliable control of the motion of magnetic domainwalls; a key requirement for the development of novel classes of logic and storagedevices. Part One introduces the design and synthesis of magnetic nanowires andmicrowires, reviewing the growth and processing of nanowires and nanowireheterostructures using such methods as sol-gel and electrodepositioncombinations, focused-electron/ion-beam-induced deposition, chemicalvapour transport, quenching and drawing and magnetic interactions. Magneticand transport properties, alongside domain walls, in nano- and microwiresare then explored in Part Two, before Part Three goes on to explore a widerange of applications for magnetic nano- and microwire devices, includingmemory, microwave and electrochemical applications, in addition to thermalspin polarization and configuration, magnetocalorific effects and Bloch pointdynamics. - Detailed coverage of multiple key techniques for the growth and processing of nanowires and microwires - Reviews the principles and difficulties involved in applying magnetic nano- and microwires to a wide range of applications - Combines the expertise of specialists from around the globe to give a broad overview of current and future trends

Controlling the magnetic anisotropy at buried interfaces has become an increasingly important topic as the areal density in magnetic storage media such as hard disk drives (HDD) continues to increase. High density storage demands tailored structures to obtain the desired material properties, so do magnetic random access memory (MRAM) and spin torque oscillators (STO). These structures are often created by layering individual materials and using the interface interactions to tune the material properties, such as the magnetic anisotropy, magnetic switching field, and magnetic thermal stability. Additionally, the fundamental physics behind interface interactions, such as exchange bias and graded magnetic anisotropy, have not been fully explored. Thus, this line of research fulfills important scientific and technological goals. Graded magnetic anisotropy promises a way of decoupling the thermal stability of a magnetic element from the required applied field to switch it. This is of prime importance because the thermal stability of magnetic elements is compromised as they become smaller. To overcome this, the typical solution is to increase the magnetic anisotropy of the element, which, in turn, increases the switching field. If the magnetic bit can be made thermally stable while maintaining a low switching field, then it is possible to switch the element with a compact write head. In practice, graded magnetic anisotropy media have not been studied thoroughly. In this dissertation, a comprehensive set of depth dependent magnetic measurements, as well as structural characterizations, were carried out on the Co/Pd multilayer system. The first-order reversal curve (FORC) technique is applied extensively to identify reversal mechanisms and different reversal phases within the material. In particular, the extension of the FORC technique to x-ray magnetic circular dichroism (XMCD) as a surface sensitive technique that identifies reversible magnetization change was performed for the first time. Polarized neutron reflectivity (PNR) was also used to directly measure the magnetization as a function of depth. The effects of deposition pressure grading within the Co/Pd multilayers were investigated. Structures were graded with three distinct pressure regions. FORC analysis shows that not only does increasing the deposition pressure increase the coercivity and effective anisotropy within that region, but also the order in which the pressure is changed also affects the entire structure. Layers grown at high sputtering pressures tend to reverse via domain wall pinning and rotation while those grown at lower pressures reverse via rapid domain wall propagation laterally across the film. Having high pressure layers underneath low pressure layers causes disorder to vertically propagate and lessen the induced anisotropy gradient. This analysis is confirmed by depth dependent magnetization profiles obtain from PNR. Continuously pressure-graded Co/Pd multilayers were then sputtered at two incident angles onto porous aluminum oxide templates with different pore aspect ratios. The effects of pressure grading versus uniform low pressure deposition is studied, as well as the effect of the angle of the incident deposition flux. The coercivity of the pressure graded perpendicular flux sample is compared to the low pressure sample. Additionally the effect of deposition angle and pore sidewall deposition is investigated. It is shown that sidewall deposition strongly affects the reversal behavior. As another way to induce a vertical anisotropy gradient, Co/Pd multilayers were bombarded with Ar+ ions at different energies and fluences. The effects of the depth dependent structural damage as a function of irradiation conditions were investigated. It is shown that the structural damage weakens the perpendicular anisotropy of the surface layers, causing a tilting of the surface magnetic moment into the plane of the film. The surface behavior is explicitly measured and shown to have a significant tilting angle in the top 5 nm depending on irradiation energy and fluence. Continuing the study of vertical anisotropy gradients in Co/Pd multilayers, multilayers with varied Co thickness were studied. Four films with varying Co thickness profiles were created and then patterned into nanodot arrays with diameters between 700 nm and 70 nm. The different films were graded continuously, or in stacks with varying Co thicknesses. An anisotropy gradient is shown to be established in the graded samples, and the switching field is lowered as a result. Furthermore, in the continuously graded samples the magnetization reversal behavior is fundamentally different from all other samples. The thermal energy barriers are measured in the uniform and continuously graded samples, yielding similar results. Finally, the establishment of exchange anisotropy at the ferromagnet / antiferromagnet (FM/AFM) interface in the epitaxial Fe/CoO system is investigated as a function of AFM thickness. The establishment of frozen AFM moments is analyzed using the FORC technique. The FORC technique combined with vector coil measurements also shows the transition from rotatable AFM to pinned AFM moments and suggests a mechanism of winding domain walls within the bulk AFM.