STUDY OF MAGNON-POLARITON USING PLANAR RESONATOR

• Main Author: Hanafi, Imam
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/63288
• Institution: Institut Teknologi Bandung

Quantum technology has flourished rapidly which is potentially be applicable to quantum information and communication. The design of modern devices that pioneer quantum information and communication technology is closely related to the interaction between waves and matters. Some researchers have shown the existence of strong interaction between waves and matters using various instrument setup. Such strong interaction gives rise to polaritons i.e. quasi particles which have wave-like and matter-like nature. One kind of polaritons that have been widely known is magnon-polaritons. These quasi particles formed from interaction between magnon (a set of exited spins) and photons. The efficiency of transfer of energy between spins contained in materials with photons can be identified by determining the coupling strength between both. The interaction of these quantities can be controlled by means of certain methods, one of which is controlling the external field imposed on materials. Such controllable interaction provides powerful way to access and control the state of systems which is useful in quantum information and communication technology. In application level, the phenomenon of strong interaction between magnon and photon requires a specific device that can produce photon resonance and magnetic resonance. Photon resonance is obtained by using resonators in the form of cavity resonators or planar resonators while magnetic resonance is obtained using a saturatedly magnetic material. Several previous studies have been carried out using 3D and planar-based resonators and using YIG materials and their derivatives in the form of bulk or thin film single-crystal. The usage of YIG as a source of magnon is based on the nature of the material which has a high spin density and very low damping which allows magnon to propagate as far as several hundred centimeters in samples, so that this material is widely used in microwave-based devices. The usage of single-crystal YIG materials is based on the well-ordered of the atoms in the sample that magnon as the excited mode can be identified as well as FMR as the fundamental mode. So far, the authors have not yet found an instrumentation setup that uses YIG polycrystal as a magnon source, this makes chance to be explored further. Although the 3D-based resonator has a better factor quality than the planar resonator, the use of this 3D resonator is considered less applicative at dimension perspective when compared to planar resonator. In addition, planar resonators are easier to define the working frequency as needed. Therefore, in this study, an instrument was developed to access the strong interaction of magnons and photons using a planar-based resonator made of PCB substrate with a dielectric constant of 6.15 and using YIG material as a source of FMR/magnon. The instrument that used to interact waves and matter is planar based resonator which has dimensional advantages when compared to cavity-based resonator. This research has several objectives: to develop instrument that mediate strong interaction between waves and matters, to know resonance frequency, quality factor, intrinsic loss resonator, Gilbert damping, coupling strength and strength constant system. To this end, yttrium iron garnet (YIG) sample is used as magnon source, SRR (split ring resonator) to produce photon mode. This study uses quantitative approach which all tested parameters are expressed to numerical terms. Since quantitative approach is used in this study that the appropriate method for this research is experimental method. This research has several objectives including to develop an instrument to access the strong interaction of wave and material, to know the resonant frequency of the system, the quality factor, the intrinsic loss of the resonator, Gilbert damping and coupling strength and coupling constant. For this purpose, polycrystalline yttrium iron garnet (YIG) samples were used as a source of FMR/magnon and SRR (split ring resonator) to produce photon modes. The approach used in this study is a quantitative which all the parameters tested are expressed in the form of numbers. Because of using a quantitative approach, the method that is suitable for this research is the experimental method. The measurements to the YIG-SRR system using VNA conducted at the Radar Laboratory, STEI ITB, our instrument can generate photon resonance at frequencies of 1.98 GHz, 4.0 GHz and 5.79 GHz with quality factors (and intrinsic loss) at each of the above frequencies are 412.37, 130.99 and 101.37 (and 0.002419, 0.007837 and 0.010029). The developed instrument can also generate magnetic resonance related to YIG materials which can be identified easily by applying external magnetic field where this resonance depends on the applied field, this is clearly a characteristic of magnetic resonance. It generates three magnetic resonances that are sensitive to a given magnetic field. By changing the applied external magnetic field, the magnetic resonance shifts to a higher frequency while the resonance of resonator remains constant except when the magnetic resonance approaches the resonance of resonator at frequency around of 4 GHz, resonance of resonator also shifts towards a higher frequency. The dispersion relation curve of resonance as a function of the magnetic field shows an anti-crossing curve that indicating there has been a strong interaction between photons and FMR/magnon. It is known that the magnitude of the strong interaction (interaction constant) yielded is 0.6833 ± 0.0131 GHz (0.1723 ± 0.0033), this value is 10.4 times greater than those done by Zhang et al, in 2017 which used bulk YIG single crystal and planar resonator. Other quantities related to the YIG sample are the anisotropy field, magnetization and gyromagnetic ratio as well as the Gilbert damping, each of which is ±0.727 Oe, which is one time larger than reported, 205.99 Oe ± 97.44Oe (8.5 times smaller), 4.169 MHz/Oe ± 0.192 MHz/Oe (1.5 times larger) and 6.064% ± 2.09% (60.6 times larger).