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

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 2 Outline Transmission line basics Step response --- time-domain reflectometry (TDR) measurement Pulse response Time-domain transmission (TDT) measurement Examples

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 3 Transmission line basics V+V+ x I+I+ V-V- I-I- u=c/n Characteristic impedance Usually, Z 0 =50 . Ground Signal

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 4 Transmission line basics Voltage reflection coefficient Current reflection coefficient V+V+ I+I+ V-V- I-I- ZLZL Z0Z0

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 5 Step response --- time-domain reflectometry (TDR) measurement Terminated with Z 0 Z0Z0 Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) T= /u t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( )

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 6 Z0Z0 Z0Z0 x 0 /2 Z0Z0 V(x) t=0 + T= /u I(x) V(x) t=T - I(x) V(x) t=2T I(x)

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 7 Step response --- time-domain reflectometry (TDR) measurement Open circuit Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) T= /u t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 8 Z0Z0 x 0 /2 Z0Z0 V(x) t=0 + T= /u I(x) V(x) t=T - I(x) V(x) t=T + I(x) V(x) t=3T/2 I(x) V - (x) I - (x)

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 9 Step response --- time-domain reflectometry (TDR) measurement Short circuit Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR T= /u

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 10 Step response --- time-domain reflectometry (TDR) measurement Capacitive load Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) T= /u t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 11 Step response --- time-domain reflectometry (TDR) measurement Inductive load Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) T= /u t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 12 Step response --- time-domain reflectometry (TDR) measurement Resistive load Z0Z0 V0V0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR RLRL

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 13 Capacitance and Inductance Capacitance: any contact pad with changeable electric potential relative to ground. d For SiO 2, if d=100 nm, C ox =0.345 fF/um 2. For a 100x100um 2 pad, C=3.45 pF. At 10 GHz, X c =1/2  fC=4.6 . Inductance: any wire that changeable current being passed through. I L and r in cm, and L>>r. nH For L=0.5cm, r=0.025mm, L ac =5nH. At 10 GHz, X L =2  fL=314 .

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 14 Pulse response +V 0 V0V0 tptp tptp -V 0 Using linear superposition

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 15 Short circuit Z0Z0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR T= /u Pulse response V0V0

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 16 Short circuit Z0Z0 x 0 /2 Z0Z0 V(0) t 0 t 0 T V( ) t 0 T/2 V( /2) I(0) t 0 t 0 T/2 I( /2) t 0 T I( ) 2T 3T/2 TDR T= /u Pulse response V0V0

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 17 Time-domain transmission (TDT) measurement Z0Z0 Z0Z0 V0V0 x 02 Z0Z0 V(0) t 0 t 0 2T V(2 ) T= /u t 0 T V( ) I(0) t 0 t 0 T I + ( ) t 0 2T I(2 ) RLRL R L // Z 0 I L ( ) TDR TDT ILIL

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 18 Time-domain transmission (TDT) measurement Z0Z0 Z0Z0 Z0Z0 RLRL ILIL V0V0 I DC V DC with DC biasing circuit suitable for 4-wire sample

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 19 Single-Shot Time-Resolved Measurements of Nanosecond-Scale Spin-Transfer Induced Switching: Stochastic Versus Deterministic Aspects T. Devolder et al, Phys. Rev. Lett. 100, (2008)

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 20 Z0Z0 Z0Z0 x 02 Z0Z0 t 0 2T V(2 ) T= /u t 0 2T I(2 ) RLRL R L +Z 0 TDT Equivalent circuit V +(2)

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 21 Time-Domain Measurements of Nanomagnet Dynamics Driven by Spin-Transfer Torques I. N. Krivorotov et al, Science 14 January :

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 22 Microwave-assisted magnetization switching of Ni 80 Fe 20 in magnetic tunnel junctions T. Moriyama et al, APPLIED PHYSICS LETTERS 90, (2007)

Yuen-Wuu Suen ( 孫允武 ) Department of Physics, NCHU 23 Spin-torque diode effect in magnetic tunnel junctions A. A. Tulapurkar et al, Nature, Vol 438|17 November 2005|doi: /nature04207