Effects of Vanadium Seed Layer in Ferrimagnetic Heusler Alloy Thin Films

Hi there! And thanks for checking out the additional information! This information is meant to be supplemental to the MIT Materials Processing Center/Center for Materials Science and Engineering Summer Internship Research Experience for Undergraduates poster presentation that I took part in on August 3, 2017.

For anyone who landed here by means other than the QR code on my research poster, take a look at the presentation below first. (Don’t worry, it’s not as complicated as it sounds.)

Effects of Vanadium Seed Layer in Ferrimagnetic Heusler Alloy Thin Films


Further and more in-depth information

First, if you are looking for more information about the research from this group, here’s a link to the website, which includes a summary of the research topic and the publications to date.

Spintronic Material and Device Group

Also, below are links to the sources that I used for my presentation.

  1. Kumar, D., Konishi, K., Kumar, N., Miwa, S., Fukushima, A., Yakushiji, K., … & Suzuki, Y. (2016). Coherent microwave generation by spintronic feedback oscillator. Scientific reports6, 30747.
  2. Žic, M., Rode, K., Thiyagarajah, N., Lau, Y. C., Betto, D., Coey, J. M. D., … & Archer, T. (2016). Designing a fully compensated half-metallic ferrimagnet. Physical Review B93(14), 140202.
  3. Felser, C., & Hirohata, A. (Eds.). (2015). Heusler Alloys: Properties, Growth, Applications (Vol. 222). Springer. p. 160.
  4. Helmich, L., Teichert, N., Hetaba, W., Behler, A., Waske, A., Klimova, S., & Huetten, A. (2015). Vanadium sacrificial layers as a novel approach for the fabrication of freestanding Heusler Shape Memory Alloys. arXiv preprint arXiv:1503.02987.
  5. Kurt, H., Rode, K., Stamenov, P., Venkatesan, M., Lau, Y. C., Fonda, E., & Coey, J. M. D. (2014). Cubic Mn 2 Ga thin films: Crossing the spin gap with ruthenium. Physical review letters112(2), 027201.

Some graphs that are notable but were not included.

vsm_compare_5samples_V1
Plot 1: VSM out-of-plane comparison of 5nm V sample with other samples from poster.

This plot shows the magnetization of a 5nm sample of vanadium compared with the samples from the poster. It was not included because the magnetization saturation value overwhelmed the other samples and distorted their graph, but the properties are notable. As you can see, the Hysteresis loop shows high saturation and some remanence, but very little coercivity, which makes it relatively unsuitable for spintronic applications. The magnetization would switch far too easily and would not lend itself to the persistent precession state necessary.

 

compare_v_mnga_v1.jpg

Plot 2: VSM out-of-plane comparison of varying V and Mn2RuxGa thickness samples.

Along the same lines, this plot shows several samples of increasing thickness of V and Heusler alloy, and varying concentration of ruthenium. Not enough samples of varying Heusler thickness and ruthenium concentration have been conducted to begin to make any conclusions, but it’s interesting to see the trends and standouts. It appears that when V and Mn2RuxGa are in a 1:1 to a 1:2 ratio, performance is fairly good, and the higher ruthenium concentration does not seem to contribute positively.

Background and topical information

If you don’t know the subject of spintronics very deeply, and you’re just curious to learn more, I’ve put together what I hope is a simple summary of some key ideas that I learned and that helped me understand exactly what it is I’ve been doing all summer. Be forewarned that this is by far and away not a comprehensive coverage of the subject, and I may actually have things a little wrong on some subjects. However, I’ve tried my best to understand each topic and explain it in simple, concise terms.

First, a little introduction to the topic.
Spintronics Introduction.png
Bonus! Great video on electron spin/precession and why it’s associated with angular momentum. https://www.youtube.com/watch?v=z_6B2M12H9w

One result of these conditions is that the steady-state precession can produce an rf microwave frequency at higher power and lower energy than conventional rf sources. In the project I worked on, we are attempting to create these devices using ferrimagnets because their precession rates are faster than ferromagnets. Another use involves random access memory (RAM). Since the parallel configuration has lower resistance than the anti-parallel, this can be used to read and write information extremely quickly. And, no, I don’t know exactly how. Hopefully, you understand RAM better than I do.

And a little bit about the materials used in the project.

Materials

Materials1
In this case, Wikipedia does a really good job. https://en.wikipedia.org/wiki/Heusler_compound
Also, these documents go deeper and also talk about Mn2RuxGa specifically.
The process of creating the thin films.

Photolithography

Magnetron sputtering

sputtering pic

Some properties of the thin films.

exchange bias

anisotropy.jpg
This is a really good, simple explanation: http://www.irm.umn.edu/hg2m/hg2m_c/hg2m_c.html
And, lastly, some methods for characterizing the films.
xrd
I watched a few videos on Bragg’s Law, and this was the best one: https://www.youtube.com/watch?v=FRDvRhCvuHg

hysteresis

hysteresis1
This is a cool, simple resource for some more details: http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/hyst.html
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s