1,721,172 research outputs found
Limited Stochastic Current for Energy-Optimized Switching of Spin-Transfer-Torque Magnetic Random-Access Memory
No full textThe switching of spin-transfer-torque magnetic random-access memory (STT MRAM) in the simple macrospin model is determined by the amplitude and pulse duration of the applied current, and it requires a current that is higher than a critical current, Ic. However, this critical current misses one fundamental physical issue for the commercialization of STT MRAM; the so-called nonswitching probability (PNS) or write soft-error rate (WSER), which is influenced by the stochastic nature of the switching process at finite temperature. Herein, we propose a limited stochastic switching (LSS) current, which is another definition for the critical current with the PNS incorporated. The definition of the LSS current and the analytical expressions are obtained by solving the Fokker-Planck equation with a given specific PNS value. Most importantly, by using the LSS current and optimizing it together with the related pulse-duration time, we find the optimum combination of current amplitude and pulse duration, which may reduce the energy consumption of the STT MRAM by up to 75%. © 2019 American Physical Society.1
Eigen damping constant of spin waves in ferromagnetic nanostructure
Get PDFThough varying in nature, all waves share traits in a way that they all follow the superposition principle while also experiencing attenuation as they propagate in space. And thus it is more than common that a comprehensive investigation of one type of wave leads to a discovery that can be extended to all kinds of waves in other fields of research. In the field of magnetism, the wave of interest corresponds to the spin wave (SW). Specifically, there has been a push to use SWs as the next information carriers similar to how electromagnetic waves are used in photonics. At present, the biggest impediment in making SW-based device to be widely adapted is the fact that the SW experiences large attenuation due to the large damping constant. Here, we developed a method to find the SW eigenmodes and show that their respective eigen damping constants can be 40% smaller than the typical material damping constant. From a bigger perspective, this finding means that the attenuation of SW and also other types of waves in general is no more constrained by the material parameters, and it can be controlled by the shape of the waves instead. © 2019, The Author(s).1
광자기·타원 분광기를 이용한 자기광학 및 자기적 성질의 연구
No full text학위논문(박사) - 한국과학기술원 : 물리학과, 1997.8, [ xi, 152 p. ]Recently, numerous important studies have been made in the field of magnetism with the current vacuum technologies and there has been a renaissance in magnetism. One of the most important field in magnetism is magneto-optical Kerr effects(MOKE). It has been attracting much attention due to applications of them as a tool in probing magnetism as well as a readout mechanism in high-density digital magneto-optical recording. Therefore, studying MOKE is very useful to understand the magnetic properties of novel magnetic materials and to implement the magneto-optical recording.
In this study, we have designed and fabricated the magneto-optical and ellipsometric spectrometer, which was essential to study magneto-optical and magnetic properties. We have combined two equipments, magneto-optic Kerr spectrometer and spectroscopic ellipsometer, into one system. Therefore, the abilities of the system were divided by two parts ;the part for the measurement of magneto-optical Kerr rotation angle and ellipticity, and the other part for determination of the complex refractive index of a sample.
Since the system was adopting a photoelastic modulator(PEM), we have studied the effects of the imperfect polarizer and analyzer in the phase-modulated magneto-optical Kerr spectrometer and spectroscopic ellipsometer using Jones matrices to represent the imperfection of the polarizer and analyzer. We have found that the polarizer and analyzer imperfections in the magneto-optical Kerr spectrometer were eliminated within the first-order approximation, because of the applied magnetic field independence. Furthermore, the polarizer and analyzer imperfections and the incorrect setting of the amplitude of the phase-modulation in the spectroscopic ellipsometer were also canceled within the first-order approximation by zone average.
We have found some new measurement methods for MOKE. First of them is to determine the off-diagonal element of the dielectric tensor, without measuring the ellipti...한국과학기술원 : 물리학과
Study on compositionally modulated Co/Pd, Co/Pt multilayers using a magneto-optic hysteresis loop tracer
No full text학위논문(석사) - 한국과학기술원 : 물리학과, 1993.2, [ iv, 77 p. ]한국과학기술원 : 물리학과
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