Domain wall pinning dependent on nanomagnet state

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Dec 1, 2013 (3 years and 8 months ago)

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© 2009 IBM Corporation

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

©
2013
IBM Corporation

Domain wall pinning dependent on
nanomagnet

state

Reinier van Mourik
1,2
, Charles Rettner
1
,
Bert
Koopmans
2
,
Stuart
Parkin
1


1. IBM
Almaden

Research Center, San Jose, CA

2. Eindhoven University of Technology, Eindhoven, the Netherlands


BB
-
03


IBM Research

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.



IBM Research

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

IBM Research

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

𝑀

𝑀

𝐻

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


Domain wall injection line


Hall bar

pulser

H

AMR

Hall bar

0

H
dep

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

𝑀

𝑀

𝐻

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


Domain wall injection line


Hall bar

pulser

H

AMR

Hall bar

0

H
dep

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

IBM Research

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

©
2013
IBM Corporation

Discussion

Micromagnetic

energy calculation


DW fine structure introduces asymmetric component in energy
landscape so
𝑑𝐸
/
𝑑𝑥

𝐻
𝑝

is higher in right
-
magnetized case.

-
200

-
100

0

100

200

-
1.5

-
1

-
0.5

0

0.5

1

DW position [nm]

energy [aJ]

top view

side view

IBM Research

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

©
2013
IBM Corporation

Application

Application potential

H
probe

𝐻


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 high

AMR low

IBM Research

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