DOCSLIB.ORG

Giant Magnetoresistance (GMR) –Spin Filtering and Spin Momentum Transfer

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Giant Magnetoresistance (GMR) –Spin Filtering and Spin Momentum Transfer NYU NYU Spins Dynamics in Nanomagnets Outline I. Spin-Transport and Transfer Basics Andrew D. Kent –Giant magnetoresistance (GMR) –Spin filtering and spin momentum transfer II. Spin-Transfer Induced Magnetization Dynamics Department of Physics, New York University –Landau-Lifshitz-Gilbert dynamics and spin-torque –Current threshold for excitations and stability diagrams III. Experiments Lecture 1: Magnetic Interactions and Classical Magnetization –Point contacts, nanopillars Dynamics –dc transport, noise, high frequency characteristics Lecture 2: Spin Current Induced Magnetization Dynamics IV. Spin-Transfer MRAM Lecture 3: Quantum Spin Dynamics in Molecular Nanomagnets –Ultimate miniaturization of MRAM V. Summary References !"#$%&'()#*#+,)#-)./'()-)"+/#0$#1(2"3)(&4/#&(0'5#.()#6%/57.8)6#97)$+:#+0&)+,)(#;%+,#+,0/)#0$#<)(+4/# &(0'5#9(%&,+:=#>,)#8?.@%/#."6#@?.@%/#()5()/)"+#+,)#()/%/+."A)#A,."&)#."6#)@+)(".7#-.&")+%A#$%)76B#()/5)A? 1 2009 Boulder+%C)78=# School,>,)# Lecture)@5)(%- 2 )"+/#/,0;#.#-0/+#/%&"%$%A."+#")&.+%C)#-.&")+0()/%/+."A)#$0(#+,)#+(%7.8)(#./#;)77#./# 2 2009 Boulder School, Lecture 2 Physics 2007+,)#-'7+%7.8)(/=#>,)#/8/+)-/#+0#+,)#(%&,+B#%"C07C%"&#7.(&)#/+.AD/#0$#7.8)(/B#/,0;#.#6)A()./10/15/2007)#0$#()/% 08:19/+." APM)# 38#.7-0/+#EFG#;,)"#/'3H)A+)6#+0#.#-.&")+%A#$%)76=#>,)#)$$)A+#%/#-'A,#/-.77)(#$0(#+,)#/8/+)-#+0#+,)# 7)$+B#"0+#0"78#3)A.'/)#+,)#/8/+)-#%/#-)()78#.#+(%7.8)(#3'+#.7/0#3)A.'/)#+,)#)@5)(%-)"+/#7)6#38#1(2"3)(&# ;)()#-.6)#.+#(00-#+)-5)(.+'()B#;,%7)#+,)#)@5)(%-)"+/#()50(+)6#38#<)(+#."6#A0?;0(D)(/#;)()#5)(? $0(-)6#.+#CGiant)(8#70;#+)- 5Magnetoresistance)(.+'()#9I=*J:=# (GMR) Giant Magnetoresistance (GMR) # 1988 The Nobel Prize in Physics 2007 !"#$%&'()#*#+,)#-)./'()-)"+/#0$#1(2"3)(&4/#&(0'5#.()#6%/57.8)6#97)$+:#+0&)+,)(#;%+,#+,0/)#0$#<)(+4/# &(0'5#9(%&,+:=#>,)#8?.@%/#."6#@?.@%/#()5()/)"+#+,)#()/%/+."A)#A,."&)#."6#)@+)(".7#-.&")+%A#$%)76B#()/5)A? "for the discovery of Giant Magnetoresistance" +%C)78=#>,)#)@5)(%-)"+/#/,0;#.#-0/+#/%&"%$%A."+#")&.+%C)#-.&")+0()/%/+."A)#$0(#+,)H#+(%7.8)(#./#;)77#./# GMR=5.4 % at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hoto: © Forschungszentrum Photo: B. Fert, Invisuphoto M)$+N#O.&")+0()/%/+."A)#-)./'()-)"+/#Jülich9L:#9(00-#+)-5)(.+'():#$0(#+,)#+(%7.8)(#/8/+)-#<)PQ(P<)=#>0#+,)#$.(#(%&,+#./#;)77#./#+0# +,)#$.(#7)$+#+,)#-.&")+%R.+%0"/#0$#+,)#+;0#%(0"#7.8)(/#.()#30+,#5.(.77)7#+0#+,)#)@+)(".7#-.&")+%A#$%)76=#!"#+,)#%"+)(-)6%.+)#()? Albert&%0 "Fert#+,)#-.&")+%R.+%0Peter"/#0 $Grünberg#+,)#+;0#%(0"#7.8)(/#.()#."+%5.(.77)7=#>,)#)@5)(%-)"+/#.7/0#/,0;#.#,8/+)(%/%/#3),.C%0'(#96%$$)()"A)# 1/2S#. of" 6the#I #prize9*#."6#L::#+85% A1/2.7# of$0 the(#- prize.&")+%R.+%0"#-)./'()-)"+/=# T%&,+N#O.&")+0()/%/+."A)#-)./'()-)"+/#9I:#9I=*J:#$0(#+,)#-'7+%7.8)(#/8/+)-#9<)PQ(:"#=#>0#+,)#$.(#(%&,+#9UVW#B#;,)()#VW#%/# France Germany +,)#/.+'(.+%0"#$%)76:#./#;)77#./#+0#+,)#$.(#7)$+#9X#Y#VW#:#+,)#-.&")+%R.+%0"/#0$#.77#%(0"#7.8)(/#.()#5.(.77)7#+0#+,)#)@+)(".7#-.&? ")+%A#$%)76=#!"#+,)#70;#$%)76#()&%0"#)C)(8#/)A0"6#%(0"#7.8)(#%/#-.&")+%R)6#."+%5.(.77)7#+0#+,)#)@+)(".7#-.&")+%A#$%)76=#SF#D1#Z# Université Paris-Sud; Forschungszentrum Jülich Differential Resistance UnitéS# >Mixte)/7 .de=# Physique Jülich, Germany CNRS/THALES Orsay,# France b. 19381(2"3)(&#9L:#.7/0#b.()50(+)6# 1939 70;#+)-5)(.+'()#-.&")+0()/%/+."A)#-)./'()-)"+/#$0(#.#/8/+)-#;%+,#+,())# %(0"#7.8)(/#/)5.(.+)6#38#+;0#A,(0-%'-#7.8)(/#."6#$0'"6#.#()/%/+."A)#6)A()./)#0$#SFG=# # # # Titles, data‘Spintronics’= and places given above refer to the time Spin of the award.+Transport+Electr<%&'()#*=#K$+)(#()$/onics=#9L:#."6#9I:: =#control# of current [0+#0"78#6%6#<)(+#."6#1(2"3)(&#-)./'()#/+(0"&78#M)$+N#)",."A)6#O.&")+0()/%/+."A)#-.&")+0()/%/+-)./'()-%C%+%)/B#)"+/#9L:#3'+#9(+,)8#00-#+).7/0#-5)(.+'():#%6)"+%? $0(#+,)#+(%7.8)(#/8/+)-#<)PQ(P<)=#>0#+,)#$.(#(%&,+#./#;)77#./#+0# About $%)6#+,)/)#03/)(C.+%0"/#./#.#");#5,)"0-Nobelprize.orgusing Privacy the Policy spinTerms of Use of Technical electrons Support )RSS"0"B#;,)()#+, )#$.(#7)The+,)#0(%&%"#0$#+,)#-$+# Official+,)#- Web.& "Site)+ %ofR .the+% 0Nobel"/.#0 &")+0()/%/+."A)#;./#0$#.#+0?Foundation$#+,)#+; 0Copyright#%(0"#7 .©8 Nobel)(/# .Web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http://nobelprize.org/nobel_prizes/physics/laureates/2007/ # Page 1 of 1 >,)#6%/A0C)(8#0$#&%."+#-.&")+0()/%/+."A)#%--)6%.+)78#05)")6#+,)#600(#+0#.#;).7+,#0$#");#/A%)"+%$%A#."6# +)A,"070&%A.7#50//%3%7%+%)/B#%"A7'6%"&#.#+()-)"60'/#%"$7')"A)#0"#+,)#+)A,"%^')#0$#6.+.#/+0(.&)#."6#-.&")+%A# /)"/0(/=#>,0'/."6/#0$#/A%)"+%/+/#.77#.(0'"6#+,)#;0(76#.()#+06.8#;0(D%"&#0"#-.&")+0)7)A+(0"%A#5,)"0-)".# ."6#+,)%(#)@570(.+%0"=#>,)#/+0(8#0$#+,)#1OT#)$$)A+#%/#.#C)(8#&006#6)-0"/+(.+%0"#0$#,0;#.#+0+.778#'")@? 5)A+)6#/A%)"+%$%A#6%/A0C)(8#A."#&%C)#(%/)#+0#A0-57)+)78#");#+)A,"070&%)/#."6#A0--)(A%.7#5(06'A+/=# *#9SE:# # Magnetoresistance (MR) !R/R The Two Channel Model of GMR Spin-dependent scattering of conduction electrons & change of scattering rate with an external field. Cu 0 [Ar].3d10.4s1 Cu [a.u.] Co DOS 0 [Ar].3d7.4s2 " e e" 0 E-EF ! ! Rspin-down = Rspin-up MR ! 0 Co Resistance Rparallel << Ranti-parallel Rspin-down > Rspin-up MR ~ 1 % " R/R ~ 1-10 % " M e e" ! ! Key Idea!!! Spin Filtering by Ferromagnetic Layers If a magnetic layer acts as a spin-filter, then Parallel Antiparallel it must also experience a torque. low resistance state high resistance state Torque # % " ! # $ I sin% Ferromagnetic layers act spin polarizers and analyzers for an electric current! Slonczewski 1996 and Berger 1996 Seeds of the idea in Slonczewski, PRB 1989 Torques with Two Magnetic Layers Reversing the direction of the current Electron flow (negative current) changes the sign of the torque fixed free Spin currents moving to the Torque # right exert a torque favoring parallel alignment % " (and a low resistance state) Electron flow (positive current) ! Spin currents moving to the left fixed free exert a torque favoring antiparallel alignment (and a high resistance state) # $ I sin% Spin-transfer is an interface effect: 2π Transverse spin coherence length: λc = kf↑ − kf↓ Stiles and Zangwill, PRB 2002 Spin Transfer – A new method to manipulate nanomagnets Dynamics: LLG+spin-torque (LLGS) Spin current induced switching, Coherent dynamic precession. dmˆ dmˆ = −γmˆ × H" eff + αmˆ × + γaJ mˆ × (ˆm × mˆ P ) Charge current dt dt Spin current ! Heff damping [ˆm (ˆm mˆ )ˆm] − p − · p hP¯ J “fixed” ferromagnet aJ = mˆ 2eMst normal metal layer Spin-torque When the spin-torque exceeds “free” ferromagnet the damping, instabilities can precession occur! ! Also possible: bJ mˆ × mˆ P mˆ × Heff C. Oersted, 1819 J.C. Slonczewski, 1996 ‘Current-Induced Effective field’ γ/2π = 28 GHz/T z y New Physics: Thin film elements ! Insight into spin transport: injection, diffusion and coherence x ! Fundamentally new types of magnetic excitations ! Most of the theories are still untested H! = H! M (ˆm zˆ)ˆz + H (ˆm xˆ)ˆx eff − eff · K · Magnetic Excitations Stability Diagrams 2e α ! In-plane magnetization and field: J = M t(H + H +2πM ) c P s K eff mˆ ! H! H PS P P/AP AP J 2e α ! Perpendicular magnetization and field: Jc = Mst(H 4πMeff ) ! P − 8 H>4πMeff H 4πM P/AP K ! eff ! 6 P Spin-current amplifies the motion for currents greater than a critical value: H 4 AP/PS AP 2e α mˆ Jc = Mst(H + HK +2πMeff) 2 PS ! P Applied Field [T] 0 0 0.05 0.1 J.
Load more

Recommended publications
  • Recent Developments of Magnetoresistive Sensors for Industrial Applications
    Sensors 2015, 15, 28665-28689; doi:10.3390/s151128665 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Review Recent Developments of Magnetoresistive Sensors for Industrial Applications Lisa Jogschies, Daniel Klaas, Rahel Kruppe, Johannes Rittinger, Piriya Taptimthong, Anja Wienecke, Lutz Rissing and Marc Christopher Wurz * Institute of Micro Production Technology, Centre for Production Technology, Leibniz Universitaet Hannover, Garbsen 30823, Germany; E-Mails: [email protected] (L.J.); [email protected] (D.K.); [email protected] (R.K.); [email protected] (J.R.); [email protected] (P.T.); [email protected] (A.W.); [email protected] (L.R.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +49-511-762-7486; Fax: +49-511-762-2867. Academic Editor: Andreas Hütten Received: 31 August 2015 / Accepted: 5 November 2015 / Published: 12 November 2015 Abstract: The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling).
    [Show full text]
  • Perspectives of Giant Magnetoresistance
    published in Solid State Physics, ed. by H. Ehrenreich and F. Spaepen, Vol. 56 (Academic Press, 2001) pp.113-237 Perspectives of Giant Magnetoresistance E.Y.Tsymbal and D.G.Pettifor Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK I. Introduction II. Origin of GMR 1. Spin-dependent conductivity 2. Role of band structure 3. Resistor model III. Experimental survey 4. Composition dependence 5. Nonmagnetic layer thickness dependence 6. Magnetic layer thickness dependence 7. Roughness dependence 8. Impurity dependence 9. Outer-boundary dependence 10. Temperature dependence 11. Angular dependence IV. Free-electron and simple tight-binding models 12. Semiclassical theory 13. Quantum-mechanical theory 14. Tight-binding models V. Multiband models 15. Ballistic limit 16. Semiclassical theory 17. Tight-binding models 18. First-principle models VI. CPP GMR VII. Conclusions 1 I. INTRODUCTION the GMR effect.9 In these materials ferromagnetic precipitates are embedded in a non-magnetic host metal film. The randomly-oriented magnetic moments of the precipitates can be aligned by the Giant magnetoresistance (GMR) is one of the most fascinating discoveries in thin-film applied magnetic field which results in a resistance drop. The various types of systems in which GMR magnetism, which combines both tremendous technological potential and deep fundamental physics. is observed are shown in Fig.2. Within a decade of GMR being discovered in 1988 commercial devices based on this phenomenon, such as hard-disk read-heads, magnetic field sensors and magnetic memory chips, had become R available in the market. These achievements would not have been possible without a detailed R understanding of the physics of GMR, which requires a quantum-mechanical insight into the a AP electronic spin-dependent transport in magnetic structures.
    [Show full text]
  • High Sensitivity Differential Giant Magnetoresistance (GMR) Based Sensor for Non-Contacting DC/AC Current Measurement
    Article High Sensitivity Differential Giant Magnetoresistance (GMR) Based Sensor for Non-Contacting DC/AC Current Measurement Cristian Mușuroi, Mihai Oproiu, Marius Volmer * and Ioana Firastrau 1 Department of Electrical Engineering and Applied Physics, Transilvania University of Brasov, 29 Blvd. Eroilor, 500036 Brasov, Romania; [email protected] (C.M.); [email protected] (M.O.); [email protected] (I.F.) * Correspondence: [email protected] Received: 10 December 2019; Accepted: 3 January 2020; Published: 6 January 2020 Abstract: This paper presents the design and implementation of a high sensitivity giant magnetoresistance (GMR) based current sensor with a broad range of applications. The novelty of our approach consists in using a double differential measurement system, based on commercial GMR sensors, with an adjustable biasing system used to linearize the field response of the system. The work aims to act as a fully-operational proof of concept application, with an emphasis on the mode of operation and methods to improve the sensitivity and linearity of the measurement system. The implemented system has a broad current measurement range from as low as 75 mA in DC and 150 mA in AC up to 4 A by using a single setup. The sensor system is also very low power, consuming only 6.4 mW. Due to the way the sensors are polarized and positioned above the U- shaped conductive band through which the current to be measured is flowing, the differential setup offers a sensitivity of about between 0.0272 to 0.0307 V/A (signal from sensors with no amplifications), a high immunity to external magnetic fields, low hysteresis effects of 40 mA, and a temperature drift of the offset of about −2.59×10−4 A/°C.
    [Show full text]
  • Shubnikov-De Haas-Like Quantum Oscillations in Artificial One
    Shubnikov-de Haas-like Quantum Oscillations in Artificial One-Dimensional LaAlO3/SrTiO3 Electron Channels Guanglei Cheng1,2,3,5, Anil Annadi2,3, Shicheng Lu2,3, Hyungwoo Lee4, Jung-Woo Lee4, Mengchen Huang2,3, Chang-Beom Eom4, Patrick Irvin2,3 and Jeremy Levy2,3* 1CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China 2Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA. 3Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA. 4Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA. 5Hefei National Laboratory for Physical Sciences, Hefei 230026, China * E-mail: [email protected] Abstract: The widely reported magnetoresistance oscillations in LaAlO3/SrTiO3 heterostructures have invariably been attributed to the Shubnikov-de Haas (SdH) effect, despite a pronounced inconsistency with low-field Hall resistance measurements. Here we report SdH-like resistance oscillations in quasi-1D electron waveguides created at the LaAlO3/SrTiO3 interface by conductive atomic force microscopy lithography. These oscillations can be directly attributed to magnetic depopulation of magnetoelectric subbands. Our results suggest that the SdH oscillations in 2D SrTiO3-based systems may originate from naturally forming quasi-1D channels. SrTiO3-based interfaces, and in particular the LaAlO3/SrTiO3 (LAO/STO) interface [1], combine the motif of semiconductor heterostructures such as GaAs/AlGaAs, with the wide- ranging physical phenomena of complex-oxides. The LAO/STO system exhibits a wide range of gate-tunable phenomena including superconductivity [2,3], magnetism [4], spin-orbit coupling [5,6] and electron pairing without superconductivity [7].
    [Show full text]
  • Integrated Giant Magnetoresistance Technology for Approachable Weak Biomagnetic Signal Detections
    Review Integrated Giant Magnetoresistance Technology for Approachable Weak Biomagnetic Signal Detections Hui-Min Shen 1, Liang Hu 2,* and Xin Fu 2 1 School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; [email protected] 2 State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310028, China; [email protected] * Correspondence: [email protected]; Tel.: +86-571-8795-3395 Received: 26 November 2017; Accepted: 5 January 2018; Published: 7 January 2018 Abstract: With the extensive applications of biomagnetic signals derived from active biological tissue in both clinical diagnoses and human-computer-interaction, there is an increasing need for approachable weak biomagnetic sensing technology. The inherent merits of giant magnetoresistance (GMR) and its high integration with multiple technologies makes it possible to detect weak biomagnetic signals with micron-sized, non-cooled and low-cost sensors, considering that the magnetic field intensity attenuates rapidly with distance. This paper focuses on the state-of-art in integrated GMR technology for approachable biomagnetic sensing from the perspective of discipline fusion between them. The progress in integrated GMR to overcome the challenges in weak biomagnetic signal detection towards high resolution portable applications is addressed. The various strategies for 1/f noise reduction and sensitivity enhancement in integrated GMR technology for sub-pT biomagnetic signal recording are discussed. In this paper, we review the developments of integrated GMR technology for in vivo/vitro biomagnetic source imaging and demonstrate how integrated GMR can be utilized for biomagnetic field detection. Since the field sensitivity of integrated GMR technology is being pushed to fT/Hz0.5 with the focused efforts, it is believed that the potential of integrated GMR technology will make it preferred choice in weak biomagnetic signal detection in the future.
    [Show full text]
  • 1 Large Linear Magnetoresistance and Shubnikov-De Hass
    Large Linear Magnetoresistance and Shubnikov-de Hass Oscillations in Single Crystals of YPdBi Heusler Topological Insulators Wenhong Wang 1, Yin Du1, Guizhou Xu1, Xiaoming Zhang1, Enke Liu1, Zhongyuan Liu 2,Youguo Shi1, Jinglan Chen1, Guangheng Wu1, and Xixiang Zhang3 1 State Key Laboratory for Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2 State Key Laboratory of Metastable Material Sciences and Technology, Yanshan University, Qinhuangdao 066004, P. R. China 3 Core Labs, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia We report the observation of a large linear magnetoresistance (MR) and Shubnikov-de Hass (SdH) quantum oscillations in single crystals of YPdBi Heusler topological insulators. Owning to the successfully obtained the high-quality YPdBi single crystals, large non-saturating linear MR of as high as 350% at 5K and over 120% at 300 K under a moderate magnetic field of 7 T is observed. In addition to the large, field-linear MR, the samples exhibit pronounced SdH quantum oscillations at low temperature. Analysis of the SdH data manifests that the high-mobility bulk electron carriers dominate the magnetotransport and are responsible for the observed large linear MR in YPdBi crystals. These findings imply that the Heusler-based topological insulators have superiorities for investigating the novel quantum transport properties and developing the potential applications. 1 Materials exhibiting large linear magnetoresistance (MR) have attracted intense research interest due to their potential applications in magnetic random access memory and magnetic sensors1. The MR of non-magnetic metals with open Fermi surfaces (e.g., Au) can be linear and non-saturating at high fields2.
    [Show full text]
  • Advance in Magnetoresistance Magnetometer Performances Applied in Eddy Current Sensor Arrays
    ADVANCE IN MAGNETORESISTANCE MAGNETOMETER PERFORMANCES APPLIED IN EDDY CURRENT SENSOR ARRAYS. L.Perez1, C.Dolabdjian1, W.Waché2, L.Butin2 1 GREYC UMR 6072 - ENSICAEN and University of Caen Basse-Normandie 2 CEGELEC, CNDT, Brétigny S/Orge Cedex France Abstract: The sensitivity of the magnetic sensor is important for many electromagnetic Non Destructive Evaluation (NDE) applications. Nevertheless, for successful defect detection, properties such as high linearity, large dynamic range and good spatial resolution are required. One solution comes in good using improved solid- state magnetic sensors based on Giant MagnetoResistance (GMR). In this way, we have implemented and improved elementary GMR magnetometer in order to develop NDE Eddy Current System (ECS) sensor arrays [1]. Elementary sensor operates in unshielded environment with very good performances, like high bandwidth (f > 100 kHz), very high slew-rate (> 30 T/s), high intrinsic dynamic (> 140 dB/√Hz at 100 Hz) and low total harmonic distortion (< 0.03 %). We compare their performances to some magnetic field sensors implemented in NDE System, focusing on the state of the art of high sensitivity magnetometer experimental investigation. The improved GMR magnetometer replaces here the detection coil used in conventional ECS, which is surrounding by an excitation setup using a classical coil. Besides the determination of its experimental performances in alternating current techniques or remanent field measurement, we present the implementation of improved GMR magnetometer dedicated to the measurement of deep lying cracks in conducting material like aluminum and ferromagnetic plates. Introduction: Classically, ElectroMagnetic NonDestructive Evaluation is based on probing local anomalies in the magnetic of the object under test or electromagnetic stray field of the object under test.
    [Show full text]
  • Extraordinary Magnetoresistance Effect in Semiconductor/Metal Hybrid Structures
    Extraordinary Magnetoresistance Effect in Semiconductor/Metal Hybrid Structures Dissertation by Jian Sun In Partial Fulfillment of the Requirements For the Degree of Doctor of Philosophy King Abdullah University of Science and Technology Thuwal, Kingdom of Saudi Arabia July 2013 2 EXAMINATION COMMITTEE APPROVALS FORM The dissertation of Jian Sun is approved by the examination committee. Committee Chairperson: Dr. Jürgen Kosel Committee Member: Dr. Dirk Grundler Committee Member: Dr. Ian Foulds Committee Member: Dr. Markus Hadwiger 3 © 2013 Jian Sun All Rights Reserved 4 ABSTRACT Extraordinary Magnetoresistance Effect in Semiconductor/Metal Hybrid Structures Jian Sun In this dissertation, the extraordinary magnetoresistance (EMR) effect in semiconductor/metal hybrid structures is studied to improve the performance in sensing applications. Using two-dimensional finite element simulations, the geometric dependence of the output sensitivity, which is a more relevant parameter for EMR sensors than the magnetoresistance (MR), is studied. The results show that the optimal geometry in this case is different from the geometry reported before, where the MR ratio was optimized. A device consisting of a semiconductor bar with length/width ratio of 5~10 and having only 2 contacts is found to exhibit the highest sensitivity. A newly developed three-dimensional finite element model is employed to investigate parameters that have been neglected with the two dimensional simulations utilized so far, i.e., thickness of metal shunt and arbitrary semiconductor/metal interface. The simulations show the influence of those parameters on the sensitivity is up to 10 %. The model also enables exploring the EMR effect in planar magnetic fields. In case of a bar device, the sensitivity to planar fields is about 15 % to 20 % of the one to perpendicular fields.
    [Show full text]
  • Magnetoresistance of N-Type Magnesium Germanide Soo Nyong Lee Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1968 Magnetoresistance of n-type magnesium germanide Soo Nyong Lee Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Condensed Matter Physics Commons Recommended Citation Lee, Soo Nyong, "Magnetoresistance of n-type magnesium germanide " (1968). Retrospective Theses and Dissertations. 4607. https://lib.dr.iastate.edu/rtd/4607 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been microfilmed exactly as received 69-9870 LEE, Soo Nyong, 1936- MAGNETORESISTANCE OF N-TYPE MAGNESIUM GERMANIDE. Iowa State University, Ph.D., 1968 Physics, solid state University Microfilms, Inc., Ann Arbor, Michigan MAGNETORESISTANCE OF N-TYPE MAGNESIUM GERMANIDE by Soo Nyong Lee A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Physics Approved: Signature was redacted for privacy. In Charg of Major Work Signature was redacted for privacy. Signature was redacted for privacy. Iowa State University Ames, Iowa 1968 ii TABLE OF CONTENTS ABSTRACT iii INTRODUCTION 1 A. Magnetoresistance 1 B. Properties of Mg^Ge 3 C. Purpose of This Investigation 8 THEORY 9 A. Magnetoconductivity Tensor Components 9 B. Experimental Approach 14 C. Energy Surfaces of the Many-Valley Type 17 EXPERIMENTAL PROCEDURE 28 A.
    [Show full text]
  • Harvesting Heat Through Seebeck Spin Tunneling Effect
    Harvesting Heat through Seebeck Spin Tunneling Effect Costel Constantin James Madison University Science Enabled by Photon Source, May 2012 Outline 1. Spintronics vs. Spin Caloritronics. 2. Novel Spin Caloritronics Device. 3. Introduction to Seebeck Effect. 4. TiO2 Nanolayer Growth by Atomic Layer Deposition and Preliminary Results. 5. Thermoelectric and Optical Studies of PEDOT-PSS/Glass substrates. Spintronics What is spintronics? -The ability of using the electron’s spin as an information carrier. How can we do that? One needs a spin injection mechanism (a transfer of spin from one material to another). 1. By sandwiching a nonmagnetic metal between two ferromagnetic materials. This is called giant magnetoresistance system 2. By creating a so called Dilute Magnetic Semiconductors (DMS) also called ferromagnetic semiconductors. Fig. 1 Giant Magnetoresistance system Fig. 2 Dilute Magnetic Semiconductor Problems with DMS materials 1. Maintaining ferromagnetism (Tc) at or above 300K? So far manganese gallium arsenide (MnGaAs) can only reach Tc ~ 173 K [1]. Other suitable candidates need to be explored. 2. Avoiding clustering of the magnetic atoms. It is very common that manganese atoms would like to cluster together rather then be randomly distributed throughout the entire crystal structure. Muhammad B. Haider, Costel Constantin, Hamad Al-Brithen, Haiqiang Yang, Eugen Trifan, David C. Ingram, and Arthur R. Smith, C.V. Kelly and Y. Ijiri, "Ga/N flux ratio influence on Mn incorporation, surface morphology, and lattice polarity during radio frequency molecular-beam epitaxy of (Ga,Mn)N," J. Appl. Phys. 93(9), 5274, (2003). We found that either metal-rich or N-rich conditions are necessary for achieving substitutional Mn incorporation on the Ga sites.
    [Show full text]
  • The Discovery of Giant Magnetoresistance
    9 October 2007 Scientific Background on the Nobel Prize in Physics 2007 The Discovery of Giant Magnetoresistance compiled by the Class for Physics of the Royal Swedish Academy of Sciences ____________________________________________________________________________________________________ The Royal Swedish Academy of Sciences, Information Department, Box 50005, SE-104 05 Stockholm, Sweden Phone: +46 8 673 95 00, Fax: +46 8 15 56 70, E-mail: [email protected], Website: www.kva.se Nobel Prize® and the Nobel Prize® medal design mark are registered trademarks of the Nobel Foundation 1. Introduction The phenomenon called magnetoresistance (MR) is the change of resistance of a conductor when it is placed in an external magnetic field. For ferromagnets like iron, cobalt and nickel this property will also depend on the direction of the external field relative to the direction of the current through the magnet. Exactly 150 years ago W. Thomson (1) (Lord Kelvin) measured the behaviour of the resis- tance of iron and nickel in the presence of a magnetic field. He wrote “I found that iron, when sub- jected to a magnetic force, acquires an increase of resistance to the conduction of electricity along, and a diminution of resistance to the conduction of electricity across, the lines of magnetization”. This dif- ference in resistance between the parallel and perpendicular case is called anisotropic magnetoresis- tance (AMR) (2). It is now known that this property originates from the electron spin-orbit coupling. In general magnetoresistance effects are very small, at most of the order of a few per cent. The MR effect has been of substantial importance technologically, especially in connection with read- out heads for magnetic disks and as sensors of magnetic fields.
    [Show full text]
  • A Size Threshold for Enhanced Magnetoresistance in Colloidally Prepared Cofe2o4 Nanoparticle Solids Benjamin H
    This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Research Article Cite This: ACS Cent. Sci. 2018, 4, 1222−1227 http://pubs.acs.org/journal/acscii A Size Threshold for Enhanced Magnetoresistance in Colloidally Prepared CoFe2O4 Nanoparticle Solids Benjamin H. Zhou† and Jeffrey D. Rinehart*,†,‡ † ‡ Materials Science and Engineering Program and Department of Chemistry and Biochemistry, University of CaliforniaSan Diego, La Jolla, California 92093, United States *S Supporting Information ABSTRACT: The phenomenon of granular magnetoresist- ance offers the promise of rapid functional materials discovery and high-sensitivity, low-cost sensing technology. Since its discovery over 25 years ago, a major challenge has been the preparation of solids composed of well-characterized, uniform, nanoscale magnetic domains. Rapid advances in colloidal nanochemistry now facilitate the study of more complex and finely controlled materials, enabling the rigorous exploration of the fundamental nature and maximal capabilities of this intriguing class of spintronic materials. We present the first study of size-dependence in granular magnetoresistance using colloidal nanoparticles. These data demonstrate a strongly nonlinear size-dependent magnetoresistance with smaller particles having strong ΔR/R ∼ 18% at 300 K and larger particles ff showing a 3-fold decline. Importantly, this indicates that CoFe2O4 can act as an e ective room temperature granular magnetoresistor and that neither a high superparamagnetic blocking temperature nor a low overall resistance are determining factors in viable magnetoresistance values for sensing applications. These results demonstrate the promise of wider exploration of nontraditional granular structures composed of nanomaterials, molecule-based magnets, and metal-organic frameworks.
    [Show full text]