• Title/Summary/Keyword: Coercive field

Search Result 349, Processing Time 0.024 seconds

Study on the Coercive Field Strenght Noise Depends on The Magnetic Field Annealing Effect of Amorphous Ribbon (비정질 리본의 자기장중 열처리에 의한 보자력 노이즈의 변화에 관한 연구)

  • 최근화;손대락
    • Journal of the Korean Magnetics Society
    • /
    • v.4 no.2
    • /
    • pp.150-153
    • /
    • 1994
  • Magnetic field annealing method has been used to obtain proper hysteresis loop shapes which are useful to a device using amorphous ribbon. In this study, two pairs of Helmhotz coils were used to apply longitudinal and transverse magnetic field during annealing. For the measurement of coercive field strength noise which depends on magnetic field annealing, Co-based amorphous alloy ribbon $VITROVAC^{\circledR}$ 6030 was used. For the sample which was annealed under dc transverse and dc longitudinal magnetic field, coercive field strength noise was nearly independent of magnetizing frequency ranging from 1 to 100 kHz, but dc transverse and ac longitudinal magnetic fields annealed samples show that the coercive field strength noise decreased in power of magnetizing frequency. When magnetic domain nucleation occurred, the coercive field strength noise increased remarkably and decreased in power of magnetizing frequency.

  • PDF

A study on hysteresis and temperature properties of VDF/TrFe copolymer (VDF/TrFE 공중합체의 히스테리시스 및 온도특성)

  • 방태찬;김종경;강대하
    • Electrical & Electronic Materials
    • /
    • v.10 no.2
    • /
    • pp.156-165
    • /
    • 1997
  • D-E hysteresis loops have been measured for the 65/35 mole % copolymer of vinylidene fluoride and trifluoroethylene over wide temperature range. The remanent polarization and the coercive field at room temperature were estimated to be 75 mC/m$^{2}$ and 55 MV/m respectively. D-E hysteresis loops were observed even below the glass transition temperature(-20.deg. C) and the remanent polarization and the coercive field were larger, as the temperature lower. It seems that the remanent polarization and the coercive field depend on the amorphous region as well as crystalline region in this copolymer. And the ferroelectric-to-paraelectric phase transition was observed at 90.deg. C on heating and 80'C on cooling. Double hysteresis loops were observed at the temperature(85.deg. C) of paraelectric phase.

  • PDF

Magnetic Creep in Narrow Channel (좁은 Channel에서의 자기적 Creep)

  • 박영문
    • 전기의세계
    • /
    • v.23 no.2
    • /
    • pp.55-61
    • /
    • 1974
  • Nature of magnetic creep phenomena in low coercive force films(Ni 80%-Fe 20%) in form of narrow channels imbedded in high coercive force films is studied in this work. Aluminium is evaporated on the hot glass substrate and eched free in the shape of narrow channels by photoetoetching method. then, Permalloy(Ni 80%, Fe 20%) is deposited on these Aluminium substrate under the uniform field of 30(Oe) to introduce anisotropy. Permalloy film on Al has a high coercive force and one on the substrate devoid of Al has how coercive force. Magnetic revers domain which is introduced at the end of channel grows under the a.c field in hard axis direction, in spite of very weak d.c field in easy axis direction. This creeping is investigated as a function of external fields and channel widths. Permalloy film thickness is 500.angs.-900.angs. and channel widths are 40, 51, 65, 81, 115.mu. respectively. Creeping increases as external field increases while it decreases with channel width decrease. Creep velocity in channels depends on the a.c field along hard axis, d.c field along easy axis and channel widths and its range is 1-10cm/sec in this experiment. From study of dependence of creep velocity on channel width, it can be concluded that creep velocity is expressed in form of v=v$_{0}$ exp .alpha.(H-H$_{0}$) where .alpha. is a function of a.c field along hard axis and H is driving d.c field along easy axis, H$_{0}$ is not a coercive force of film as usuall expected but the d.c threshold field along easy axis which is a function of channel width. This characteristic is also confirmed by the study of dependence of creep velocity upon easy axis field strength. Value of .alpha. obtained is 1.3-2.3cm/sec We depending upon film charactor, hard axis field strength and frequency.uency.

  • PDF

Conducting Crack Growth Behavior in Ferroelectrics Subjected to Electric Fields (전기장을 받는 강유전체 내의 전도균열 성장거동)

  • 정경문;박재연;범현규
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2002.10a
    • /
    • pp.820-823
    • /
    • 2002
  • The asymptotic problem of a semi-infinite conducting crack parallel to the poling direction in ferroelectric ceramics subjected to electric fields is analyzed. The main mechanism for the conducting crack growth behavior is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. The shape and size of the switching zone is shown to depend strongly on the relative magnitude on the ratio of the coercive electric field to the yield electric field. It is shown that the crack growth can be either enhanced or retarded depending on the ratio of the coercive electric field to yield electric field.

  • PDF

Piezoelectric and Electric Field Induced Strain Properties of PMW-PNN-PZT Ceramics with the Substitution of Ba (Ba 치환에 따른 PMW-PNN-PZT 세라믹스의 압전 및 전계유기왜형 특성)

  • 윤광희;김규수;최병수
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.14 no.1
    • /
    • pp.20-25
    • /
    • 2001
  • To develop the piezoelectric actuator, the structural, dielectric and piezoelectric properties and electric fieldinduced strain of the ceramics(Pb$\_$1-2/Ba$\_$x/)[Mg$\_$1/2/W$\_$1/2/)$\_$0.03/-Ni$\_$1/3/Nb$\_$2/3/)$\_$0.12/-(Zr$\_$0.5/Ti$\_$0.5/)$\_$0.85/]O$_3$(x=0, 0.01, 0.03, 0.05, 0.07, 0.1) were investigated with the substitution of Ba. The tetragonality of crystal structure and grain size decreased by the substitution of Ba. Curie temperature decreased due to the decrease of the tetragonality, and dielectric constants increased with the substitution of Ba. The coercive field, remnant polarization and electromechanical coupling factor also decreased, whereas the piezoelectric constatns d$\_$33/ and d$\_$31/ were showed the highest value of 430 and 209(x10$\^$-12/C/N), respectively, because of the increase of dielectric constant. The strain induced by 60Hz AC electric field had the maximum value of 204x10$\^$-6/Δℓ/ℓ at the substitution of Ba 3mol%. As the applied electric field approaches to the coercive field, the piezoelectric element is depolarized and the electric field induced strain revealed non-linearity.

  • PDF

A Study on Ferroelectric Properties of VDF/TrFE copolymer (VDF/TrFE 공중합체(共重合體)의 강유전특성(强誘電特性))

  • Bang, T.C.;Kang, D.H.
    • Proceedings of the KIEE Conference
    • /
    • 1996.07c
    • /
    • pp.1472-1475
    • /
    • 1996
  • D-E hysteresis loops have been measured for the 65/35 mole % copolymer of vinylidene fluoride and trifIuoroethyIene over wide temperature range. The results were analyzed and discussed. The remanent polarization and the coercive field at room termperature were estimated to be 75 $mC/m^3$ and 55 MV/m respectively. D-E hysteresis loops were observed even below the glass transiation temperature$-20^{\circ}C$) and the remanent polarization and the coercive field were larger than larger, as the temperature lower. It seems that the remanent polarization and the coercive field depend on the amorphous region as well as crystalline region in this copolymer. And the ferroelectric-to-paraelectric phase transition was observed at $90^{\circ}C$ on heating and $80^{\circ}C$ on cooling. Double hysteresis loops were observed at the temperature($85^{\circ}C$) of paraelectric phase.

  • PDF

Frequency Characteristics of Coercive Field in Ferroelectric Poly(Vinylidene Fluoride-Trifluoroethylene) Thin Film (강유전성 폴리(비닐리덴 플로라이드-트리플로로에틸렌) 박막의 항전계의 주파수 특성 분석)

  • Zhang, Ting;Rahman, Sheik Abdur;Khan, Shenawar Ali;Lee, Kwang-Man;Kim, Woo Young
    • Journal of the Korean Applied Science and Technology
    • /
    • v.35 no.4
    • /
    • pp.1206-1212
    • /
    • 2018
  • In this study, the polarization reversal characteristics of thin film capacitors with a thickness of 100 nm or less fabricated with ferroelectric polymer were measured and analyzed. For the fixed film thickness, polarization reversal occurred at higher coercive fields as the applied maximum electric field increased. For the fixed maximum electric field, polarization reversal occurred at the same coercive field irrespective of the thickness of the thin film. The proportional constant values between the logarithmic electric field and the logarithmic scale frequency were $0.12{\pm}0.01$ for all measurements. As a result, the ferroelectric polymer capacitors consistently exhibited polarization reversal characteristics without any size effects up to a thickness of 40 nm. This study shows the possibility of a polymer memory device that can operate at low voltage, which is useful for predicting the behavior of a low-voltage operating polymer memory device.

Electron Emission from $Pb(Zr_xTi_{1-x})O_3$ Ferroelectrics by Pulsed Electric Field (펄스 전기장에 의한 $Pb(Zr_xTi_{1-x})O_3$ 강유전체의 전자 방출)

  • 김용태;윤기현;김태희;박경봉;곽상희
    • Journal of the Korean Ceramic Society
    • /
    • v.37 no.1
    • /
    • pp.6-11
    • /
    • 2000
  • Electron emission from the Pb(ZrxTi1-x)O3 ferroelectrics by pulsed electric field has been investigated as a function of Zr/Ti ratios such as 35/65, 50/50 and 65/35 below 250kV/cm. Electrons were emitted regardless of the applied field polarity to the rear electrode. When the negative field was applied to the rear electrode, the electron emission charge was more stable. It was proved that the electrons were emitted at the edge of the upper electrode. The emission charge increased in order of 65/35>50/50>35/65. The electron emission characteristics were dependent on the ferroelectric properties such as polarization and coercive field. The emission charge and emission threshold field were affected by the polarization change and the coercive field, respectively. This result explains that the electron emission is a field emission with polarization induced surface potential by a modified Fowler-Nordheim plot of emission charge.

  • PDF

Effect of Domain Switching on Crack Growth in Ferroelectric Ceramics (분역회전이 강유전체 세라믹내의 균열성장에 미치는 영향)

  • 정경문;박재연;범현규
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.20 no.11
    • /
    • pp.142-149
    • /
    • 2003
  • Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.

Magnetic Characteristics of CoNbZr amorphous Films with Pd addition

  • Song, J.S.;Wee, S.B.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2003.05d
    • /
    • pp.90-95
    • /
    • 2003
  • The present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added as a substitution for CoNbZr alloys. The films were prepared by a RF magnetron sputtering method. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures being independent upon the amount of Pd added in the films. On the addition of 4.34% Pd, the excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in the preferred sites parallel to the external magnetic field applied on the deposition process. A permeability of about 1100 was kept constant in the operation frequency ranging up to 100 MHz, which can be explained by the Landau-Lifshitz formula.

  • PDF