Calculator Input
Example Data Table
| Example | Rₚ (Ω) | RAP (Ω) | Area (µm²) | Bias (V) | TMR (%) | RAₚ (Ω·µm²) | RAAP (Ω·µm²) |
|---|---|---|---|---|---|---|---|
| Sample MTJ Device | 120 | 210 | 0.08 | 0.05 | 75 | 9.6 | 16.8 |
| Compact Junction | 95 | 157 | 0.06 | 0.03 | 65.2632 | 5.7 | 9.42 |
| High Contrast Junction | 140 | 308 | 0.10 | 0.06 | 120 | 14 | 30.8 |
These rows illustrate how resistance states, area, and bias can be organized for quick comparison and reporting.
Formula Used
Measured TMR ratio:
TMR = (RAP - RP) / RP
TMR percentage:
TMR(%) = 100 × (RAP - RP) / RP
Jullière-model form:
TMR = 2P1P2 / (1 - P1P2)
Reverse estimation when RP is known:
RAP = RP × (1 + TMR)
Reverse estimation when RAP is known:
RP = RAP / (1 + TMR)
Use resistance mode for measured device data, polarization mode for theoretical estimates, and reverse mode when one resistance state and the TMR percentage are already known.
How to Use This Calculator
- Select the calculation mode that matches your available data.
- Enter parallel and antiparallel resistances, or provide spin polarizations, or estimate a missing resistance from known TMR.
- Optionally add junction area, bias voltage, and temperature for richer output.
- Press Calculate TMR to display results above the form.
- Review the graph, inspect the computed metrics, and export the results as CSV or PDF.
Frequently Asked Questions
1) What does TMR mean here?
TMR here means tunnel magnetoresistance. It measures how much a magnetic tunnel junction changes resistance when the magnetizations switch between parallel and antiparallel alignment.
2) Why is the parallel resistance usually lower?
In many magnetic tunnel junctions, electron tunneling is more favorable when electrode magnetizations are parallel. That usually gives a lower resistance than the antiparallel state.
3) What is a good TMR percentage?
A good value depends on materials, barrier quality, temperature, and fabrication. Higher TMR generally indicates stronger contrast between states and better switching readout.
4) When should I use polarization mode?
Use polarization mode when you know or want to test theoretical spin polarizations instead of measured resistances. It helps estimate idealized TMR behavior.
5) What is the RA product?
The RA product is resistance multiplied by junction area. It is useful for comparing tunnel junctions of different sizes on a more consistent basis.
6) Can TMR be negative?
Yes. If the antiparallel resistance becomes lower than the parallel resistance, the calculated TMR ratio becomes negative. That can happen in special material systems or measurement conditions.
7) Why include bias voltage?
Bias voltage lets the calculator estimate current in each state using Ohm’s law. That is useful for comparing read conditions and signal levels.
8) What does the graph show?
The graph compares the resistance states used or estimated in the selected mode. It makes switching contrast easier to inspect visually before exporting results.