Hyuk Won

A Study on the Deperm Protocols Considering Demagnetizing Field of a Ferromagnetic Material

(Received 23 September 2013, Received in final form 7 March 2014, Accepted 14 March 2014)Magnetic materials with large coercive force and high squareness ratio are currently developing to meet anindustrial demand. Since a ferromagnetic material has hysteresis characteristics, it is hard to demagnetize aferromagnetic material precisely. In this paper, we describe deperm processes and conduct an analysis ofresidual magnetization of ferromagnetic material using the Preisach modeling with a two-dimensional finiteelements method (FEM). From the results, it was shown that an exponential decrement form of depermprotocol is more efficient than a linear decrement form because of the demagnetizing field in the ferromagneticmaterial. Keywords : deperm, ferromagnetic material, preisach model, Anhysteretic Deperm, Deperm-ME, demagnetizationeffect, FEM

Eddy current effects on the high density magnetic recording system

The frequency of the recording current and the rotating speed of the recording media are increased for the high densities in perpendicular magnetic recording system with high conductive pole tip head and soft magnetic under-layer. In this paper, the frequency induced eddy current and velocity induced eddy currents are analyzed by nonlinear three-dimensional finite element analysis. It turns out that the frequency induced eddy current decreases the amplitude of the recording fields, whereas the velocity induced eddy current only distorts the distribution of the recording fields in the recording media

A Study on the Deperm of Ferromagnetic Material using Preisach Model

Ferromagnetic material`s residual magnetization is remained because of the interaction between domains from external apply field, so the electrical and electronic industry and area of defense development request deperm protocol which makes the residual magnetization to 0. But the deperm protocols which are used theses days are developed by using only experience and experiment, so we have to develop deperm protocol considering hysteresis curve. In this paper, Anhysteretic Deperm, Deperm-ME, Flash-Deperm were analyzed using two dimensional finite element method and Preisach model that was formulated by property of magnetic materials. From that analysis, the relations between hysteresis curve and deperm variable are compared by analyzing the trace of Preisach plane. Also, an efficient current ratio of deperm protocol, is proposed.

A Study of Improved Convergence on the Preisach Model Method by Using M-B Variables

It is necessary to describe the hysteresis characteristics of magnetic material precisely for the analysis or design of system with ferromagnetic materials. Although Preisach model is regarded as the most accurate method to describe the hysteresis characteristics, it is not widely applied to the real systems because of some difficulties. The conventional Preisach model shows the numerical instabilities during the iterative computations because the density distribution obtained from the sets of M-H curves are strongly localized. To remove such numerical instabilities, M-B instead of M-H is adopted as an implementation variable in normal Preisach modeling. The two dimensional computations with hysteresis characteristics by using normal Preisach modeling are tested and the result showed that the modeling by using M-B variables showed better stabilities than M-H variables.

Analysis and measurement of the magnetophoretic display system by using bistable magnetic ball for extremely low power consumptions

This paper is about novel designed magnetophoretic display system that is using bistable magnetic ball. Nowadays, it must is most of important issue that is efficient using energy and saving energy in the common problem. When display system is refreshing the display, it need a energy source but it will have not been needed any energy for continued displayed display.

Magnetic hysteresis modeling in perpendicular MRAM system for high Gb/Chip

In this paper, we present a micromagnetic analysis of the new MRAM system for high Gb/Chip. Proposed MRAM has a strong switching field owing to two poles added on both sides of the free layer, just like perpendicular magnetic recording heads on the hard disk drive system. By comparing conventional MRAM and new MRAM, we show that new MRAM has a strong switching field on the same injected current.

Introduction and analysis of the MRAM with pole type system by using micromagnetic approach for high Gb/Chip

In this paper, new MRAM designs for high Gb/Chip with pole system was introduced. In order to overcome problem of reducing power consumption, we proposed new MRAM design that has two additional high permeable poles. Proposed new MRAM designs has a strong switching field owing to two poles added on both sides of the free layer, just like perpendicular magnetic recording heads.

Proposal of a Novel Pole Type Structures in Perpendicular MRAM for High Gb/Chip

This paper proposes a novel MRAM using perpendicular magnetic tunnel junction device for high capacity. Conventional MRAM has weak points to realize high capacity in the design structure of the cell, one of which is that using simple current injection system can generate only weak switching field. As a solution, we propose a novel MRAM that has two additional poles in this paper. Proposed novel MRAM has a strong switching field owing to two poles added on both sides of the free layer, just like perpendicular magnetic recording heads. In this paper, analysis of the switching field and useful designs for high Gb/Chip are presented. This research was done using three dimensional FEM with injected current density of 8 times 107 A/cm2 -6 times 108 A/cm2.

Research of Optimal MRAM Adding Pole for High Gb/Chip

Magnetoresistive random access memory (MRAM) don`t get very public face on the field of non-volatile memory. Because recording capacity of MRAM is smaller than other non-volatile memory and structurally, magnetic efficiency of MRAM is very bad. We diminish a size of one cell in order to make MRAM of high recording capacity. But It don`t make high recording field in general structures consisting of two current wire. Accordingly, We make a cell of small size is impossible. In this paper, we suggest new MRAM that it have two pole of high permeability on both ends of recording layer. Because magnetic efficiency of new MRAM is higher than exiting MRAM, it can make high recording field. And we can diminish the size of one cell due to recording layer of high coercivity. We used three-dimension finite element method to prove the reliability.

Eddy Current Effects on the High Density Magnetic Recording System

The frequency of the recording current and the rotating speed of the recording media are Increase for the high densities in perpendicular magnetic recording system with high conductive pole tip head and soft magnetic under-layer. In the paper, the frequency Induced eddy current and velocity induced eddy currents are analyzed by non-linear 3-dimensional finite element analysis. It it turned out that the frequency induced eddy current decreases the amplitude of the recording fields, whereas the velocity induced eddy current only distorts the distribution of the recording fields in the recording media.