Papers by Conrad Rizal, PhD
Biosensors and Bioelectronics, 2024
Sensors utilizing magneto-optical surface plasmon resonance are gaining increasing scientific and... more Sensors utilizing magneto-optical surface plasmon resonance are gaining increasing scientific and practical attention to detect atmospheric gases and humidity. The magneto-optic surface plasmon resonance wavelength is defined by the plasmonic structure's geometry and structure, making it immune to electromagnetic interference outside its resonance frequency range. The present study investigates their application for the detection of atmospheric gases including humidity. In contrast to conventional sensors, magneto-optic sensors exhibited excellent performance in terms of sensitivity (10 times greater), higher quality factor (up to 76 times higher) and design simplicity in terms of layer thickness optimization, integration, and robustness. These results suggest significant potential for utilization of magneto-optic sensors across multiple industries.
Obtaining highly sensitive ferromagnetic, FM, and nonmagnetic, NM, multilayers with a large room-... more Obtaining highly sensitive ferromagnetic, FM, and nonmagnetic, NM, multilayers with a large room-temperature magnetoresistance, MR, and strong magnetic anisotropy, MA, under a small externally applied magnetic field, H, remains a subject of scientific and technical interest. Recent advances in nanofabrication and characterization techniques have further opened up several new ways through which MR, sensitivity to H, and MA of the FM/NM multilayers could be dramatically improved in miniature devices such as smart spin-valves based biosensors, non-volatile magnetic random access memory, and spin transfer torque nano-oscillators. This review presents in detail the fabrication and characterization of a few representative FM/NM multilayered films—including the nature and origin of MR, mechanism associated with spin-dependent conductivity and artificial generation of MA. In particular, a special attention is given to the Pulsed-current deposition technique and on the potential industrial applications and future prospects. FM multilayers presented in this review are already used in real-life applications such as magnetic sensors in automobile and computer industries. These material are extremely important as they have the capability to efficiently replace presently used magnetic sensors in automobile, electronics, biophysics, and medicine, among many others.
Bio-Magnetoplasmonics, is a relatively new science and it merges three fields of science: nanop... more Bio-Magnetoplasmonics, is a relatively new science and it merges three fields of science: nanoplasmonics, nano-mangetism, and nano-photonics, where biological samples are made to interact with surface plasmonic wave fields, also referred to as evanescent radiation fields.
DESCRIPTION In-plane magnetism and MR of the e-beam evaporated multilayers
International Journal of Applied Physics and Mathematics, 2011
A series of Fe-Co alloys were produced at the atomic scale, onto 15 nm Cu buffer layers, using pu... more A series of Fe-Co alloys were produced at the atomic scale, onto 15 nm Cu buffer layers, using pulsed-current deposition. The relationship between saturation magnetization, M s and lattice constant, a has been investigated. The effects of increasing stacking number (bilayer number) on the values of M s and a have been examined. The alloys showed a maximum room temperature M s of 240 emu/g at 25 at. % Co . A study to the room temperature magnetic and microstructure analysis revealed that the increase in saturation magnetization strongly correlates with the lattice constant of the Fe-Co alloy.
Fe/Cu multilayer films were prepared using pulsed-current electro-deposition method. The role of ... more Fe/Cu multilayer films were prepared using pulsed-current electro-deposition method. The role of the pulsed-current deposition and Fe and Cu layer thicknesses on the magnetic properties was investigated. The micro-structure of the multilayer films is dependent on the thicknesses of both the Fe and Cu layers. The saturation magnetization of the multilayers strongly correlated with the crystalline structure of Fe at the interface of Fe and Cu layers.
JNEP
When suitably alloyed, ferromagnetic-nonmagnetic (FM-NM) and ferromagnetic-ferromagnetic (FM-FM) ... more When suitably alloyed, ferromagnetic-nonmagnetic (FM-NM) and ferromagnetic-ferromagnetic (FM-FM) 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 easy of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application.
We report on the magnetic anisotropy and magnetoresistance properties of Co/Au multilayers prepar... more We report on the magnetic anisotropy and magnetoresistance properties of Co/Au multilayers prepared by changing the incident angle of deposition,theta, the thicknesses of Co and Au layers respectively, and the number of bilayers, N while keeping N times tCo fixed at 20 nm. Although all of the multilayers showed magnetic anisotropies at low applied magnetic fields, H, and at room temperature, the ones deposited at theta = 45 degree showed remarkable mgnetic anisotropies, which is further enhanced upon magnetic annealing. The Co/Au multilayer showed a maximum magnetoresistance of 2.1 % at room temperature and H=1 kOe. Moreover, for the same field H and current I, the transverse magnetoresistance is always larger than the longitudinal magnetoresistance.
A series of Fe-Co alloys were produced at the atomic scale, onto 15 nm Cu buffer layers, using pu... more A series of Fe-Co alloys were produced at the atomic scale, onto 15 nm Cu buffer layers, using pulsed-current deposition. The relationship between saturation magnetization, M s and lattice constant, a has been investigated. The effects of increasing stacking number (bilayer number) on the values of M s and a have been examined. The alloys showed a maximum room temperature M s of 240 emu/g at 25 at. % Co . A study to the room temperature magnetic and microstructure analysis revealed that the increase in saturation magnetization strongly correlates with the lattice constant of the Fe-Co alloy.
[Co (t Co) nm/Cu 1.5 nm]50multilayers were grown onto 15-nm Cu/polyimide buffer layers. The relat... more [Co (t Co) nm/Cu 1.5 nm]50multilayers were grown onto 15-nm Cu/polyimide buffer layers. The relationship between stress, σ, and strain, ɛ, for the [Co 1.0 nm/Cu 1.5 nm]50multilayers has been presented. The effects of induced strain on the magnetoresistance(MR) and magnetic anisotropy have been examined. The [Co 1.0 nm/Cu 1.5 nm]50multilayer exhibited a maximum MR ratio of 3.4% at a Co layer thickness of 1.0 nm, β of 0.1, and a strain of 1.5%. The multilayers exhibited a remarkable magnetic anisotropy with the easy axis of magnetization always lying in a plane perpendicular to the direction of the induced strain.
A series of e-beam evaporated [Co10 Å/Aut Å]20 multilayers has been deposited on 1.69 mm2 glass s... more A series of e-beam evaporated [Co10 Å/Aut Å]20 multilayers has been deposited on 1.69 mm2 glass substrates. The samples were examined with vibrating sample magnetometer, low angle X-ray diffraction, and magnetoresistance (MR) measurements. The effects of oblique incidence evaporation and magnetic annealing on the anisotropy, microstructure, and different components of MR are examined. After magnetic annealing, the multilayer [Co10 Å/Au20 Å]20 produced at the incidence angle of 45° showed a strong anisotropy and the easy axis of the anisotropy is along the perpendicular (x-axis; along the film plane) to the incidence of evaporation. MR at room temperature has two components: isotropic and anisotropic. The magnetoresistance effects are found to be larger in the uniaxial films, with both anisotropic and giant magnetoresistance peaking at around 20 Å Au layer thickness.
We have investigated the relationship between the magnetism and the magnetoresistance effect in t... more We have investigated the relationship between the magnetism and the magnetoresistance effect in the Co/Au, Ag multilayer films with layers produced in the atomic level by pulse electrodeposition method. The magnetoresistance effect is dependent on both the thickness of Co ferromagnetic layer and Ag,Au non-magnetic layers. The magnetization of these films shows the minimum value against the Ag and Au layer thickness. The Ag and Au layer thickness showing the maximum of MR ratio is not of necessary in
agreement with the Ag and Au layer thickness showing the minimum of magnetization. Antiparallel alignment of magnetic spin is a necessary but not sufficient condition in order to generate the GMR of multilayer films. For the Co/Au multilayer films, the Au layer thickness showing the minimum of the magnetization shifts to higher side of the Au layer thickness.
Conference Presentations by Conrad Rizal, PhD
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Papers by Conrad Rizal, PhD
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 easy of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application.
agreement with the Ag and Au layer thickness showing the minimum of magnetization. Antiparallel alignment of magnetic spin is a necessary but not sufficient condition in order to generate the GMR of multilayer films. For the Co/Au multilayer films, the Au layer thickness showing the minimum of the magnetization shifts to higher side of the Au layer thickness.
Conference Presentations by Conrad Rizal, PhD
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 easy of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application.
agreement with the Ag and Au layer thickness showing the minimum of magnetization. Antiparallel alignment of magnetic spin is a necessary but not sufficient condition in order to generate the GMR of multilayer films. For the Co/Au multilayer films, the Au layer thickness showing the minimum of the magnetization shifts to higher side of the Au layer thickness.