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Spin Dependent Transport

Eran Maniv  
Instructor of the SDT experiment

 

Room: Kaplun Basement 013

Telephone.gif Phone: 03-640-8286

Em_anm.gif Email: eranmaniv@mail.tau.ac.il


 

Contents:

  1. Introduction
  2. Topics of the experiment
  3. How to prepare for the experiment?
  4. The experimental schedule
  5. Literature
  6. Links

 

Introduction:

In magnetic media, charge carrier transport (electron or hole) is found to depend on the spin orientation of the carrier. Several such phenomena will be measured:


Anomalous Hall Effect (AHE) - When applying an external magnetic field perpendicular to a thin film, and running a transport current along the film, a transverse voltage (normal to both field and current) is detected. This is the Hall voltage. The Hall voltage has two components: (1) The normal contribution due to the Lorentz force acting on the charge carriers. (2) The AHE component which depends on the spin orientation of the charge carriers. 

Anisotropic magnetoresistance (AMR) - Dependence of electrical resistance in ferromagnetic metals on the direction of magnetization relative to the current. 

Giant Magnetoresistance (GMR) - A dramatic change in resistance due to application of external magnetic field (much larger than AMR) is found in samples of alternating ferromagnetic and non magnetic layers, or in samples of magnetic nano grains, coated by non magnetic material. Recently, Albert Fert and Peter Grunberg recieved the 2007 Physics Nobel Prize for the discovery of GMR. Scientific background can be found in http://www.nobelprize.org/nobel_prizes/physics/laureates/2007/grunberg-lecture.html. Currently, GMR is used in hard drive read heads.
 

 

Topics of the experiment:

  • Understanding the basics of magneto-transport measurements (symmetry of signal with respect to applied field...).
  • Observation of EHE ,AMR and GMR.
  • Extracting quantities such as the sign and density of charge carriers in Nickel.

 

How to prepare for the experiment?

  1. Read the relevant literature: 
    1. Magnetism I - From: Introduction to magnetism and magnetic materials, by David Jiles
    2. Magnetism II - From: Introduction to magnetism and magnetic materials, by David Jiles
    3. Spin dependent transport - From: Modern magnetic materials, principles and applications, by Robert C. O'Handley
    4. GMR, EHE and four probe measurements
    5. SDT Experiment Instructions
  2. Study the experimental equipment
    1. Hewlett Packard 34401A Multimeter .
    2. Lakeshore Model 425 Gaussmeter.
  1. Learn the experiment's schedule.
  2. Make sure that you understand the experimental technique (in the experiment's instructions\measurements).
  3. Study the focus topics (in the experiment's instructions\theoretical background).

 

 

The experimental schedule:

  1. Written exam - Approximately one hour.
  2. Learning the experimental apparatus and measurements configurations.
  3. Magnetoresistance (Rxx) measurements of AgCo granular thin film and Ni thin film with the magnetic field applied perpendicular, parallel and transverse to the film.
  4. Hall (Rxy) measurements of AgCo granular thin film and Ni thin film with the magnetic field applied perpendicular to the film.
  5. Planar Hall (Rxy) measurements of Ni thin film with the magnetic field applied in the sample plane at various angles to the current.
  6. Analysis of the data using methods of symmetrizing\antisymmetrizing or the Onsager Casimir configuration.
  7. Completing necessary measurements if needed.

 

Literature:

1. Introduction to magnetism and magnetic materials, by David Jiles (pp. 1-13,27-37,38-41,69-73,219-237).

2. Modern magnetic materials, principles and applications, by Robert C. O'Handley (pp. 562-563,567-595).

3. V. D. Ky, Physica Status Solidi (b) 26, 565 (1968).

4. A. Gerber, A. Milner, I. Y. Korenblit, M. Karpovsky, A. Gladkikh, and A. Sulpice, Phys. Rev. B 57, 13667 (Jun 1998).

5. L. Onsager, Phys. Rev. 38, 2265 (Dec 1931).

6. H. B. G. Casimir, Rev. Mod. Phys. 17, 343 (Apr 1945).

 

Links:

  1. Extraordinary Hall Effect and Gaint Magnetoresistance in the Granular Co-Ag System
  2. Planar Hall Effect in Ferromagnetic Films 
  3. Giant Planar Hall Effect in Epitaxial (Ga,Mn)As Devices 

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