Ferromagnetic Alloys: Magnetoresistance, Microstructure, Magnetism, and Beyond (Review)

When suitably alloyed, ferromagnetic-nonmagnetic (FM-NM) and ferromagnetic-ferromagnetic (FMFM) alloys display remarkable saturation magnetization and magnetoresistance (MR). They also possess the ability to form well defined, unique micro and nano structures over a wide temperature range, and when prepared under closely controlled condition. This review aims to provide insights on how to synthesize macro and nano structures from the nano particles Co-Ag, Co-Cu, Co-Au, and Fe-Co alloys under controlled condition and explores magnetic and MR characteristics of thus synthesized micro and nano alloy structures - including giant MR, and saturation magnetization. Fabrication of these alloy based micro and nano structures was conducted using pulse-current deposition. Characterization was carried out using vibrating sample magnetometer, X-ray diffractometer (XRD), and rf-SQUID meter. XRD profiles and other characteristics of variously prepared nanostructures are compared in terms of particle size and lattice constant. Results suggest that both the increase in MR and saturation magnetization in FM-FM based alloys strongly depend on particle size and lattice constant in micro and nano structures. This manuscript reviews the presence of a variety of MR effects in nano-structures of FM-NM alloys and it also investigates the relationship between saturation magnetization, alloy composition, and lattice constant, also referred to as crystallographic state of the constituent element, employing phase diagram. Results presented in this review suggest that these nano-structures can potentially be employed to create next generation of bio-magnetic devices for bio-medical and electronic applications due to the ease of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application

Magnetophotonics for sensing and magnetometry toward industrial applications

Magnetic nanostructures sustaining different types of optical modes have been used for magnetometry and label-free ultrasensitive refractive index probing, where the main challenge is the realization of compact devices that are able to transfer this technology from research laboratories to smart industry. This Perspective discusses the state-of-the-art and emerging trends in realizing innovative sensors containing new architectures and materials exploiting the unique ability to actively manipulate their optical properties using an externally applied magnetic field. In addition to the well-established use of propagating and localized plasmonic fields, in the so-called magnetoplasmonics, we identified a new potential of the all-dielectric platforms for sensing to overcome losses inherent to metallic components. In describing recent advances, emphasis is placed on several feasible industrial applications, trying to give our vision on the future of this promising field of research merging optics, magnetism, and nanotechnology

Ferromagnetic Alloys: Magnetoresistance, Microstructure, Magnetism, and Beyond (Review)

When suitably alloyed, ferromagnetic-nonmagnetic (FM-NM) and ferromagnetic-ferromagnetic (FMFM) alloys display remarkable saturation magnetization and magnetoresistance (MR). They also possess the ability to form well defined, unique micro and nano structures over a wide temperature range, and when prepared under closely controlled condition. This review aims to provide insights on how to synthesize macro and nano structures from the nano particles Co-Ag, Co-Cu, Co-Au, and Fe-Co alloys under controlled condition and explores magnetic and MR characteristics of thus synthesized micro and nano alloy structures - including giant MR, and saturation magnetization. Fabrication of these alloy based micro and nano structures was conducted using pulse-current deposition. Characterization was carried out using vibrating sample magnetometer, X-ray diffractometer (XRD), and rf-SQUID meter. XRD profiles and other characteristics of variously prepared nanostructures are compared in terms of particle size and lattice constant. Results suggest that both the increase in MR and saturation magnetization in FM-FM based alloys strongly depend on particle size and lattice constant in micro and nano structures. This manuscript reviews the presence of a variety of MR effects in nano-structures of FM-NM alloys and it also investigates the relationship between saturation magnetization, alloy composition, and lattice constant, also referred to as crystallographic state of the constituent element, employing phase diagram. Results presented in this review suggest that these nano-structures can potentially be employed to create next generation of bio-magnetic devices for bio-medical and electronic applications due to the ease of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application

Surface Plasmon Resonance (SPR) to Magneto-Optic SPR

In this editorial, a brief background of the surface plasmon resonance (SPR) principle is discussed, followed by several aspects of magneto-optic SPR (MOSPR) and sensing schemes from the viewpoint of fundamental studies and potential technological applications. New sensitivity metrics are introduced that would allow researchers to compare the performance of SPR and MOSPR-based sensors. Merits of MOSPR over SPR based sensors and challenges faced by MOSPR sensors in terms of their practical use and portability are also considered. The editorial ends with potential new configurations and future prospects. This work is considered highly significant to device engineers, graduate and undergraduate students, and researchers of all levels involved in developing new classes of bio-devices for sensing, imaging, environmental monitoring, toxic gas detection, and surveying applications to name a few

Giant magnetoresistance and magnetic properties of ferromagnetic hybrid nanostructures

Significant advances in the growth, measurement, and characterization methods in the field of nanoengineering have made Co-based magnetic hybrid (ferromagnetic and non-magnetic) nanostructures increasingly important for the development of giant magnetoresistance (GMR) sensors and high magnetic-moment biocompatible nanoparticles for use in the future magnetic technology. This thesis presents the growth, measurement, and characterization of magnetic hybrid nanostructures (multilayers, alloys, and nanoparticles) that exhibit interesting magnetoresistance (MR) and magnetic properties, which are significant in the development of state-of-the-art magnetic technology for use in the electronics and biomedical sectors. Firstly, Co/Au multilayers have been grown on glass substrates using e-beam evaporation, and then Co/Ag and Co/Cu multilayers have been grown on polyimide substrates using pulsed-current deposition. All of these multilayers exhibited the GMR effect at room temperature. The maximum MR for Co/Au, Co/Ag, and Co/Cu multilayers was 2.1 %, 9.1 %, and 4.1 %, respectively. The e-beam evaporated multilayers exhibited strong magnetic anisotropy when the films were deposited at the angle of 45 degrees. The electrodeposited multilayers exhibited strong magnetic anisotropy when strain was introduced externally. In both the cases, the GMR is strongly influenced by the ferromagnetic and nonmagnetic layer thicknesses and interfacial states between layers. Secondly, novel nanocomposites Co nanoparticles embedded in Au matrix have been developed using pulsed-current deposition on polyimide substrates. They exhibited interesting MR, grain size, and saturation magnetization characteristics. The maximum room temperature GMR found was 4.6 %. X-ray diffraction, magnetization, and low temperature measurements suggest that a smaller grain size formed during higher current density correlates with the larger MR values for these nanocomposites. Thirdly, high-magnetic-moment biocompatible FeCo nanostructures have been developed using pulsed-current deposition. The nanostructures exhibited saturation magnetization of up to 240 emu/g, which is much larger than the saturation magnetization of either Co or Fe. The less expensive and highly sensitive GMR sensors if coated with specific probes, and if the target biomolecules are labelled with high-moment biocompatible nanoparticles presented in this thesis, the GMR sensors have potential for use in improving the early detection and treatment of chronic diseases (e.g., prostate and lung cancer) using biomagnetic technology.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

Magneto-Optic Surface Plasmon Resonance Ti/Au/Co/Au/Pc Configuration and Sensitivity

Magneto-optic surface plasmon resonance (MOSPR)-based sensors are highly attractive as next-generation biosensors. However, these sensors suffer from oxidation leading to degradation of performance, reproducibility of the sensor surface, because of the difficulty of removing adsorbed materials, and degradation of the sensor surface during surface cleaning and these limit their applications. In this paper, I propose MOSPR-based biosensors with 0 to 15 nm thick inert polycarbonate laminate plastic as a protective layer and theoretically demonstrate the practicability of my approach in water-medium for three different probing samples: ethanol, propanol, and pentanol. I also investigate microstructure and magnetic properties. The chemical composition and layered information of the sensor are investigated using X-ray reflectivity and X-ray diffraction analyses and these show distinct face-centered-cubic (fcc)-Au (111) phases, as dominated by the higher density of conduction electrons in Au as compared to Co. The magnetic characterization measured with the in-plane magnetic field to the sensor surface for both the as-deposited and annealed multilayers showed isotropic easy axis magnetization parallel to the multilayer interface at a saturating magnetic field of <100 Oersted (Oe). The sensor showed a maximum sensitivity of 5.5 × 104%/RIU (refractive index unit) for water–ethanol media and the highest detection level of 2.5 × 10−6 for water-pentanol media as the protective layer is increased from 0 to 15 nm

Photoluminescence Property of Eu3+ doped CaSiO3 Nano-phosphor with Controlled Grain Size

A series of Eu3+ doped CaSiO3/SiO2 nano-phosphor powder of controlled grain size, crystalline structure, and chemical composition were synthesized using the microemulsion technique. The morphology, size, and shape of the synthesized nanophosphorous powder were investigated using transmission electron microscopy and X-ray diffraction (XRD) analysis. XRD profiles of samples sintered over 600 °C, suggested phase shift from amorphous powder grain to more ordered polycrystalline powder of triclinic type wollastonite, CaSiO3, with preferred crystal phase orientation of (112) and tetragonal type cristobalites of SiO2. The grain size, crystallinity, and chemical composition of the host matrix, activator and sensitizer strongly affected both the absorption and emission bands of these samples. The amplitude of both the orange and red emission bands significantly increased with sintering temperature. The emission band is red-shifted with decreasing grain sizes. These bands displayed good sensitivity to ionic concentration of the Si4+, Ca2+, and Eu3+. With increasing Ca2+ ion concentration both the intensity of the red photoluminescence (PL) band increased and a concentration quenching observed. Increase in Si4+ ion concentration led to quenching in PL intensity of both the orange and red bands, whereas the amplitude of the blue-band slightly increased. With increasing Eu3+ ion concentration the red-band initially increased whereas it started decreasing at higher sample concentration. In the presence of Ca2+ ion as a sensitizer, the sample showed a remarkable PL property-including–about 100% photon conversion efficiency and a two-fold increase in excitation and emission photons

Design of a 2 × 4 Hybrid MMI-MZI Configuration with MMI Phase-Shifters

This paper reports design of a 2 × 4 hybrid multimode interferometer-Mach-zehnder interferometer (MMI-MZI) configuration consiting of compact thermo-optical switches on the silicon-on-insulator (SOI) platform. The device consists of two identical MMI slab waveguides as power splitters and couplers that are connected with two identical MMI-based phase shifters, and linear tapers at both ends of the MMIs to minimize the power coupling loss. A thin Al pad is used as a heating element and a trench is created around this pad to prevent heat from spreading, and to minimize loss. The calculated average thermo-optical switching power consumption, excess loss, and power imbalance are 1.4 mW, 0.9 dB, and 0.1 dB, respectively. The overall footprint of the device is 6 × 304 μm². The new heating method has advantages of compact size, ease of fabrication on SOI platform with the current CMOS technology, and offers low excess loss and power consumption as demanded by devices based on SOI technology. The device can act as two independent optical switches in one device.Applied Science, Faculty ofNon UBCElectrical and Computer Engineering, Department ofReviewedFacult

Improved Magneto-Optic Surface Plasmon Resonance Biosensors

The magneto-optic (MO) characteristics and sensing performance of noble metal (Ag, Au, Cu) or transition metal (Fe, Ni, Co) single layers and Ag/Co or Au/Co bilayers have been studied and compared in both the standard plasmonic and MO plasmonic configurations at two different wavelengths (632.8 nm and 785 nm) and in two different sensing media (air and water). The sensing performance is found to be medium-specific and lower in biosensor-relevant water-based media. The sensitivities of MO-SPR sensors is found to be superior to SPR sensors in all cases. This enhancement in sensitivity means the detection limit of this class of transducers can be substantially improved by tuning Au/Co layer thickness, wavelength, and incident angle of optical radiation. The optimized bilayer showed an enhancement in sensitivity by over 30× in air and 9× in water as compared to the conventional Au SPR configuration. Notably, the best performance is 3× above that of MO-SPR sensors coupled to a photonic crystal previously reported in the literature and is found when the ferromagnetic layer is furthest from the sensing medium, as opposed to typical MO-SPR configurations. This proposed structure is attractive for next-generation biosensors