© 2009 IBM CorporationMMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Domain wall pinning dependent on nanomagnet state

Reinier van Mourik1,2, Charles Rettner1, Bert Koopmans2, Stuart Parkin1

1. IBM Almaden Research Center, San Jose, CA2. Eindhoven University of Technology, Eindhoven, the Netherlands

BB-03

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Introduction

Magnetic Domain Walls for memory and logic

Dynamics of magnetic domain walls important for applications

Precise control of DW position required, for example by pinning

Parkin, S. S. P., M. Hayashi, et al. (2008). "Magnetic domain-wall racetrack memory." Science 320(5873): 190-194.

Memory Logic

Allwood, D. A., G. Xiong, et al. (2005). "Magnetic Domain-Wall Logic." Science 309(5741): 1688-1692.

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Introduction

Outline

Experimental setup– Domain wall pinned at and depinned from nanomagnet site

Results– Significant difference in depinning field for two nanomagnet states

Discussion– Domain wall fine structure responsible for difference

Applications– Tunable pinning site or nanomagnet readout

Conclusions

DW

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Methods

Experimental setup

AMR and Hall bar register depinning of DW

nanomagnet Py 60x90x10nm

AMR read

hall bar read

�⃑� �⃑�

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1. inject DW

2. propagate DW by H field 3. read resistance change in AMR and Hall bar

PMA [CoNi]n nanowire, 60-140nm wide

DW

Dom

ain wall injection line

Hall bar

pulser

H

AMR

Hall bar

0 Hdep

IBM Research

MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Methods

Experimental setup

Depinning field is measured for both nanomagnet states

nanomagnet Py 60x90x10nm

AMR read

hall bar read

�⃑� �⃑�

�⃑�

1. inject DW

2. propagate DW by H field 3. read resistance change in AMR and Hall bar

PMA [CoNi]n nanowire, 60-140nm wide

DW

Dom

ain wall injection line

Hall bar

pulser

H

AMR

Hall bar

0 Hdep

IBM Research

MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Results

Depinning field difference

Magnetic field required to propagate DW past nanomagnet differs by 10 mT for both states.

10 mT!

Depinning field difference increases with wire width.

typical result wire width dependence

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Discussion

Micromagnetic energy calculation

DW fine structure introduces asymmetric component in energy landscape so is higher in right-magnetized case.

-200 -100 0 100 200-1.5

-1

-0.5

0

0.5

1

DW position [nm]

ener

gy [

aJ]

top view side view

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Application

Application potential

Hprobe

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Nanomagnet acts as a DW gate if the DW is propagated at a “probe field”

Application as: – tunable DW pinning site

– nanomagnet readout

AMR high

AMR highAMR low

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MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

AMR AMR

Application

Domain wall pinning for use in NML readout

In Nanomagnetic Logic, information is propagated along arrays of nanomagnets through magnetostatic coupling.

Output magnet can be read out by DW pinning technique

Each nanomagnet can have its own nanowire.

AMR

injection line

DW

Imre, A., G. Csaba, et al. (2006). "Majority logic gate for magnetic quantum-dot cellular automata." Science 311(5758): 205-208.

IBM Research

MMM 2013 | 2013-11-05 | IBM/TUe © 2013 IBM Corporation

Conclusion

Conclusion

In-plane nanomagnet above PMA nanowire is single-magnet domain wall pinning site where the pinning strength depends on the nanomagnet state.

The depinning field can differ by 10 mT and depends on wire width.

The DW fine structure is responsible for the depinning field asymmetry.

DW pinning can be applied in logic and memory applications.

slides & contact: http://tinyurl.com/RvM-IBM