yuen-wuu suen ( 孫允武 ) department of physics, nchu 1 measuring the pulse response of magnetic...

1 Yuen-Wuu Suen (孫允武 )Department of Physics, NCHU

Measuring the Pulse Response of Magnetic Devices

Yuen-Wuu Suen (孫允武 )

Department of Physics, NCHU

---transients of transmission line circuits

2008 奈米暨前瞻光電研討會自旋電子專題2008/5/24彰化師大


Outline

Transmission line basics

Step response --- time-domain reflectometry (TDR) measurement

Pulse response

Time-domain transmission (TDT) measurement

Examples



V+

x

I+

V-I-

u=c/n

0ZI

V

I

V

Characteristic impedanceC

LZ 0 Usually, Z0=50.

)()()(

)()()(

xIxIxI

xVxVxV

Ground

Signal



Voltage reflection coefficient

Current reflection coefficient

V+

I+

V-

I-

ZL

0

0

ZZ

ZZ

L

LV

0

0

ZZ

ZZ

L

LI

II

VV

I

V

Z0



Terminated with Z0

Z0

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

T=/u

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

0


Z0

Z0

x0 /2

Z0

V(x)t=0+

T=/u

20V

0

0

2Z

V

0

I(x)

V(x)t=T- 20V

0

0

2Z

VI(x)

V(x)t=2T 2

0V

0

0

2Z

VI(x)



Open circuit

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

T=/u

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

11 IV

0V

2T

2T

3T/2

TDR


Z0

x0 /2

Z0

V(x)t=0+

T=/u

20V

0

0

2Z

V I(x)

V(x)t=T- 20V

0

0

2Z

VI(x)

V(x)t=T+ 2

0V

0

0

2Z

VI(x)

1

1

I

V

V(x)t=3T/2 2

0V

0

0

2Z

VI(x)

V-(x)

I-(x)



Short circuit

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

2T

2T

3T/2

TDR

0

0

Z

V

11 IVT=/u



Capacitive load

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

T=/u

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

0V

2T

2T

3T/2

TDR



Inductive load

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

T=/u

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

2T

2T

3T/2

TDR

0

0

Z

V



Resistive load

Z0

V0

x0 /2

Z0

V(0)

t0 t0 T

V()

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

2T

2T

3T/2

TDR

RL

0

0

ZR

ZR

L

LV

0

0

ZR

RZ

L

LI

V

ZR

R

L

L

0

2

0

2

ZR

V

L


Capacitance and Inductance

Capacitance: any contact pad with changeable electric potential relative to ground.

d d

AC r 0

For SiO2, if d=100 nm, Cox=0.345 fF/um2.For a 100x100um2 pad, C=3.45 pF.At 10 GHz, Xc=1/2fC=4.6.

Inductance: any wire that changeable current being passed through.

I

]1)/2[ln(2

]75.0)/2[ln(2

rLLL

rLLL

ac

dc L and r in cm, and L>>r.

nH

nH

For L=0.5cm, r=0.025mm, Lac=5nH.At 10 GHz, XL=2fL=314.


Pulse response

+V0

V0

tp

tp

-V0

Using linear superposition


Short circuit

Z0

x0 /2

Z0

V(0)

t0 t0 T

V()

t0 T/2

V(/2)

I(0)

t0 t0 T/2

I(/2)

t0 T

I()

20V

0

0

2Z

V

2T

2T

3T/2

TDR

0

0

Z

V

T=/u

Pulse response

V0



Z0

Z0

V0

x0 2

Z0

V(0)

t0 t0 2T

V(2)

T=/u

t0 T

V()

I(0)

t0 t0 T

I+()

t0 2T

I(2)

20V

0

0

2Z

V

RL

RL// Z0

IL()

TDR

TDT

0

0

00

00

2//

//

ZR

Z

ZZR

ZZR

LL

LV

VZR

R

VV

L

L

VL

02

2

)1(

0Z

VL

02

2

/

ZR

V

RVI

L

LLL

IL



Z0

Z0Z0RLIL

V0

IDC

VDC

with DC biasing circuit

suitable for 4-wire sample


Single-Shot Time-Resolved Measurements of Nanosecond-Scale Spin-Transfer Induced Switching: Stochastic Versus Deterministic AspectsT. Devolder et al, Phys. Rev. Lett. 100, 057206 (2008)


Z0

Z0

x0 2

Z0

t0 2T

V(2)

T=/u

t0 2T

I(2)

RL

RL+Z0

TDT

Equivalent circuit

000

00

2ZR

R

ZZR

ZZR

L

L

L

LV

VZR

ZR

VV

L

L

V

0

0

2

)(2

)1()(

VZR

RV

ZR

VI

L

LL

LL

0

0

2

2

2

2)(

V

ZR

ZV

L 0

0(2)

2

2 V+(2)

V+(2)


Time-Domain Measurements of Nanomagnet Dynamics Driven by Spin-Transfer Torques I. N. Krivorotov et al, Science 14 January 2005 307: 228-231


Microwave-assisted magnetization switching of Ni80Fe20 in magnetic tunneljunctions T. Moriyama et al, APPLIED PHYSICS LETTERS 90, 152503 (2007)


Spin-torque diode effect in magnetic tunnel junctionsA. A. Tulapurkar et al, Nature, Vol 438|17 November 2005|doi:10.1038/nature04207

yuen-wuu suen ( 孫允武 ) department of physics, nchu 1 measuring the pulse response of magnetic...

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