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Journal.qmd

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+---
+format:
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+    theme: dark.scss
+    transition: slide
+    chalkboard: true
+date: "September 14, 2022"
+---
+
+# Experimental demonstration of skyrmionic magnetic tunnel junction at room temperature
+![](2022-09-11-17-01-27.png)
+
+::: footer
+Dreycen Foiles, 9-14-2022
+:::
+
+
+## Motivation 
+
+::: {.incremental}
+
+- Skyrmions are a promising candidate for next generation information storage and processing technologies
+- Reliable electrical detection of skyrmions is one of the major hurdles preventing development of skyrmionics 
+- There are methods that make use of the anomalous Hall effect or noncollinear magnetoresistance but either produce very weak signals or would be difficult to integrate with modern electronics 
+- Using magnetic tunnel junctions (MTJ's), this paper aims to develop an electrical detection method that exploits tunnel magnetoresistance (TMR) to create a larger output signal
+:::
+
+## Skyrmion TMR Modeling {.smaller}
+
+$$ G = g_p S - \frac{\Delta g}{2} \int (1 - \cos\theta) ds $$
+
+$$ G = g_p S - \pi n_{sk} d_{sk} \Delta g w S dx$$
+
+:::: {.columns} 
+::: {.column} 
+- $g_p$ is the unit conductance
+- $S$ is the area of the MTJ
+- $\Delta g$ is the difference in conductance between parallel and anti-parallel state
+- $w$ is the effective domain wall width
+:::
+
+::: {.column} 
+
+- $\theta$ is the angle between the magnetization of the Co and CoFeB layers
+- $n_{sk}$ is the density of skyrmions 
+- $d_{sk}$ is the average diameter of a skyrmion
+::: 
+
+::::
+
+## Device Growth
+
+:::: {.columns} 
+::: {.column width="60%"}
+![](2022-09-13-15-49-16.png)
+:::
+
+::: {.column width="40%"}
+- Multilayers were fabricated with sputtering 
+- Layer compositions were confirmed using STEM
+:::
+::::
+
+
+## Device Fabrication
+
+:::: {.columns} 
+::: {.column}
+![](2022-09-13-16-05-32.png){ width=70\%}
+![](2022-09-13-16-06-43.png){ width=70\%}
+:::
+
+::: {.column}
+- The skyrmion stack was fabricated into a MTJ using photolithography and Ar ion milling
+- A lock-in amplifier paired with an AC signal generator was used to measure the TMR ratio of the MTJ (AC signal was 133.33 Hz)
+- Current pulses were used to nucleate skyrmions 
+:::
+::::
+
+## Device Characterization {.smaller}
+
+
+![](2022-09-12-22-31-39.png){fig-align="center" width=70%}
+
+- The TMR ratio was measured for different external field values
+- When the field was fully satured, the TMR ratio was zero
+- The TMR ratio was maximixed in a mixed state between skyrmions and other stripe domains
+
+
+## Device Characterization Continued {.smaller}
+
+:::: {.columns}
+
+::: {.column width=60%}
+
+![](2022-09-13-23-37-28.png)
+
+
+:::
+
+::: {.column width=40%}
+
+- The TMR ratio when the system is in the skyrmion-phase is plotted against the external field
+- The relationship between the skyrmion density and average skyrmion diameter was plotted against the applied field
+- There appears to be a more-or-less linear relationship betwee $n_{sk}$, $d_{sk}$ and the TMR ratio, which is in agreence with model
+:::
+
+::::
+
+## Neuromorphic Computing
+![](2022-09-12-22-33-18.png){fig-align="center"}
+