Measuring the Pulse Response of Magnetic Devices

Measuring the Pulse Response of Magnetic Devices ---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

Outline Transmission line basics Step response --- time-domain reflectometry (TDR) measurement Pulse response Time-domain transmission (TDT) measurement Examples

Transmission line basics u=c/n x Signal I+ I- V+ V- Ground Characteristic impedance Usually, Z0=50W.

Transmission line basics I+ I- Z0 V+ V- ZL Voltage reflection coefficient Current reflection coefficient

Step response --- time-domain reflectometry (TDR) measurement Terminated with Z0 Z0 T=l/u V0 Z0 Z0 x 0 l/2 l V(0) V(l/2) V(l) t t t 0 0 0 T/2 T I(0) I(l/2) I(l) t t t 0 0 0 T/2 T

Z0 T=l/u Z0 Z0 x 0 l/2 l V(x) t=0+ I(x) l V(x) t=T- I(x) V(x) t=2T I(x)

Step response --- time-domain reflectometry (TDR) measurement Open circuit Z0 T=l/u V0 Z0 x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l/2) I(l) t t t 0 0 0 T/2 T 2T

Z0 T=l/u Z0 x 0 l/2 l V(x) t=0+ I(x) l V(x) t=T- I(x) V-(x) V(x) t=T+ I(x) V(x) t=3T/2 I-(x) I(x)

Step response --- time-domain reflectometry (TDR) measurement Short circuit Z0 T=l/u V0 Z0 x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l) I(l/2) t t t 0 0 0 T/2 T 2T

Step response --- time-domain reflectometry (TDR) measurement Capacitive load Z0 T=l/u V0 Z0 x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l/2) I(l) t t t 0 0 0 T/2 T 2T

Step response --- time-domain reflectometry (TDR) measurement Inductive load Z0 T=l/u V0 Z0 x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l) I(l/2) t t t 0 0 0 T/2 T 2T

Step response --- time-domain reflectometry (TDR) measurement Resistive load Z0 V0 Z0 RL x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l) I(l/2) t t t 0 0 0 T/2 T 2T

Capacitance and Inductance Capacitance: any contact pad with changeable electric potential relative to ground. d For SiO2, if d=100 nm, Cox=0.345 fF/um2.For a 100x100um2 pad, C=3.45 pF.At 10 GHz, Xc=1/2pfC=4.6W. Inductance: any wire that changeable current being passed through. nH L and r in cm, and L>>r. nH For L=0.5cm, r=0.025mm, Lac=5nH.At 10 GHz, XL=2pfL=314W. I

Pulse response +V0 V0 tp tp -V0 Using linear superposition

Pulse response Short circuit Z0 T=l/u V0 Z0 x 0 l/2 l V(0) TDR V(l/2) V(l) t t t 0 0 0 T/2 T 2T 3T/2 I(0) I(l) I(l/2) t t t 0 0 0 T/2 T 2T

Time-domain transmission (TDT) measurement RL// Z0 Z0 V0 IL Z0 Z0 T=l/u RL x TDT 0 2l l V(0) V(l) V(2l) TDR t t t 0 0 0 T 2T I(0) I(2l) I+(l) IL(l) t t t 0 0 0 T 2T

Time-domain transmission (TDT) measurement with DC biasing circuit IDC VDC Z0 V0 IL Z0 Z0 RL 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)

Equivalent circuit RL+Z0 Z0 V+(2) RL Z0 Z0 T=l/u x TDT 0 2l V(2l) V+(2) t 0 2T I(2l) t 0 2T

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

Measuring the Pulse Response of Magnetic Devices

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