University of Minnesota

February 2016 Newsletter: Volume 3, Issue 1

A Message From the Director, Jian-Ping Wang

First, I have had an extremely busy but fruitful quarter for C-SPIN. I have finished my annual chat with all 33 C-SPIN PIs to get first-hand, updated information about the exciting research going in the Center. As a bonus, I also learned that our many STARnet students are doing well and moving strongly along their career paths. Two highlights stand out: Prof. Sara Majetich’s demonstration of a sub-20 nm MTJ and the efficient and coherent action of C-SPIN PIs (Profs. Ramesh, Takeuchi, Crowell, Palmstrøm, Wang, and Koester) working together to develop perpendicular Heusler alloys and integrate them with tunnel barriers, multiferrioic materials (e.g. BFO layers) and different spin channels.

This annual series of chats also allows me to discover the ways I can coordinate PIs for large group projects that address critical needs. For example, we helped Prof. Maxim Tsoi find a way to collaborate with Prof. Bhrat Jalan to grow high temperature antiferromagnetic materials and speed up his research so that he can keep his world-leading position on electrically switching antiferromagnetic materials.

Second, C-SPIN has continued to address the feedback from the 3rd annual review last September. For example, we recently recruited Prof. Tony Low (Univ. of Minnesota), a former IBMer and well-recognized SRC/NRI veteran, to work on the first-principle calculations and search for new magnetic tunnel barriers and new perpendicular Heusler alloys.

Third, we have implemented the last piece of 2.5 year re-alignment plans. We continue to be grateful for the ongoing investment of resources and time from our sponsors. We have almost settled the contract with University of Virginia to bring Prof. Jiwei Lu to grow much-needed but largely underdeveloped high-quality magneto-electrical materials and to search for novel magnetic metal-insulator-transition materials. We are also very pleased to have Prof. Kang Wang from UCLA join C-SPIN to work on antiferromagnetic memory, which is the result of a STARnet seed program.

Fourth, I would like to share with you about an interesting article about a presentation by Mr. William Holt, Intel’s general manager of technology and manufacturing, at the International Solid-State Circuits Conference in February in San Francisco. According to the chart he shares, spintronic devices have a strong position in the post-CMOS road map. This should encourage us to continue to work hard to demonstrate spintronics devices that with fast switching and low energy consumption.

Lastly, please mark your calendars for the Topological Insulator Spintronic Devices workshop on May 12 and 13 at the University of Minnesota (right after the mid-year review). Prof. Albert Fert will join the workshop and present his group’s recent efforts on topological insulator spintronics. Yes, I mean the 2007 Nobel Prize winner (Physics) for his co-discovery of Giant Magneto Resistance. Prof. Fert is an amazing scientist with a lot of information and experience that can be valuable to C-SPIN. This interview from 2014 shows dedicated Fert is to developing spintronic materials.

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C-SPIN in the Spotlight at the Joint MMM-Intermag Conference

More than ten C-SPIN PIs and nearly twenty C-SPIN students and postdoctoral fellows presented their C-SPIN research at the world's largest magnetic and spintronics conference this January in San Diego. Among them were three C-SPIN PIs who delivered prestigious invited talks on future spintronic materials and devices to more than 1,800 participants from magnetic and spintronic research institutions and industry.

• Prof. Maxim Tsoi from University of Texas at Austin, who demonstrated the world's first electrical switching of antiferromagnetic material, gave a talk on the interconnection between magnetic states and transport currents in antiferromagnetic Sr₂IrO₄.
• Prof. Christian Binek from University of Nebraska, who pioneered the research on the magnetoelectrical switching study of Cr₂O₃, gave a talk on magnetoelectric antiferromagnets for ultra-low power memory and logic and device applications.
• Prof. Geoff Beach from MIT, who co-discovered the voltage controlled magnetism on GdOx/Co bilayer structure, gave a talk on enhanced magneto-ionic switching of interface anisotropy in Pt/Co/GdOx films.

We have seen more and more researchers from STARnet companies participating and presenting exciting work at magnetic and spintronics conferences since the kickoff of C-SPIN. At this conference, Dr. Sasikanth Manipatruni from Intel, one of the world leading researchers on spin logic scaling study and a C-SPIN industry associate, presented a new and more scalable spin device concept by representing the Intel team: spin-orbit logic with magneto-electric nodes mediated by charge interconnects.

Angeline Smith, a University of Minnesota Ph.D. candidate from Prof. Jian-Ping Wang's group won a best poster award on her recent work, "Novel Spin Hall Effect Device for Perpendicular Magnetization Reversal Using a Dipole-Coupled Composite Structure." A patent application on this new concept was filed with the support of STARnet in 2015.

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Q&A with Prof. Sara Majetich, Carnegie Mellon University

From Jian-Ping Wang, C-SPIN Director: It’s no accident that Sara Majetich has been with C-SPIN from the beginning. I knew of her stellar work on nanopatterning and conductive atomic force microscopy (C-AFM), so it was easy to imagine the MTJ’s of the future being made in her lab. Below is a short Q&A between Prof. Majetich and Michael Lotti. Read it and you’ll see why I was right.

Q: Describe the C-SPIN tasks your group is working on.
A: Our work is in Theme 1. We’re focusing on conductive C-AFM measurements on MTJs that we make from materials that other C-SPIN PIs send to us. The images on the right capture our work better than anything else. They show our success making MTJs of the same size with mostly uniform magnetic properties. Still, there are slight variations, and we aren’t as small as we need to be. The goal is to make < 20 nm devices with highly uniform switching properties. Using nanoparticle masking, we have made devices as small as 7 nm, but they were not thermally stable. Today the world’s smallest working MTJs are 11 nm in diameter, and we hope to break this record.

Q: How is your C-SPIN research applicable outside of the world of computer engineering?
A: The C-AFM tool is useful as a local conductivity probe of non-magnetic materials, especially when developing new nanoscale electronic structures. It enables rapid feedback that helps optimize device design. The nanoparticle masking could be used to prepare magnetic recording media with very uniform grain sizes (and therefore lower noise) and nanopillars of many other materials. For now, other scientists will have to consider these applications: I am focused on C-SPIN and the next wave of spintronic computing technologies. We’ve come so far in the past three years, but we still have a ways to go.

Q: How has C-SPIN affected your research?
A: The Center has allowed us to do what we do best: make and test super-small devices. It’s great to be able to specialize like that while knowing that you have top-notch colleagues developing new thin films, performing theoretical analyses, and developing spintronic computing architectures. Trying to put a team like that together for a research project is almost unthinkable. In other words, C-SPIN has helped us to advance our specialized knowledge and contribute significantly to a large and hugely important project.

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Oleg Mryasov, In Memoriam

We are sad to report that our colleague Oleg Mryasov passed away from stomach cancer right after Christmas.

Oleg grew up in Yekaterinburg (in central Russia), where he was a standout student and swimmer. He received his doctoral degree in Solid State Physics from the Russian Academy of Sciences in 1993 and worked as a post-doc at Northwestern University (under Arthur Freeman) from 1993 to 1999. From 1999-2001, he held joint Research Engineer/Technical Staff appointments at UC Berkeley and Sandia National Laboratories. He joined the Seagate Research Center in 2001 as a Research Staff Member and was later promoted to Principal Research Engineer. He joined the Department of Physics & Astronomy at the University of Alabama in 2009, where he collaborated with Bill Butler on a number of projects, including several C-SPIN initiatives. In the past year, he began working as a senior scientist at Western Digital and with an adjunct appointment at the University of Minnesota.

Oleg made numerous pioneering and innovative contributions in the fields of novel CPP-GMR heterostructures with high spin polarization Heusler alloys, transparent conductors, constrained density functional theory for magnetic excitations, theory of magnetic anisotropy energy, and beyond DFT-LDA theory of metal/insulator interface states. He was awarded by the Irish Science Foundation with the C. T. Walton Fellowship grant and the Technology Achievement Award from Seagate Technology.

Oleg is survived by his wife, Elena, and two children, Nicolas and Jennifer. He is buried in Russia near his father.

From Jian-Ping Wang, C-SPIN Director: “Oleg was a valuable C-SPIN PI, a dedicated scientist, and a wonderful gentleman. I count myself lucky to have had many rich discussions with him on all aspects of magnetic materials and C-SPIN projects. After reviewing several of his classical and pioneering papers in 90s, I think that his contributions to magnetism have been underestimated.”

From Alan Kalitsov, longtime friend and research collaborator: “Oleg was a very knowledgeable scientist who was never satisfied with his achievements. Until last days of his life he had a lot of scientific plans and goals. Oleg truly believed in science and he always paid much attention to all details of his scientific projects. He was sincere, creative and passionate scientist with unbelievable endurance and enthusiasm.”

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C-SPIN Welcomes New PI, Jiwei Lu from the University of Virginia

Jiwei Lu, Research Associate Professor in the Department of Materials Science and Engineering at the University of Virginia, will explore the synthesis of a host of oxide and nitride thin films using reactive Bias Target Ion Beam Deposition (RBTIBD), a novel deposition technique. This technique provides low-energy sputter ion fluxes via end-Hall plasma sources and highly crystallized oxide thin films with very smooth surfaces. The goal is to incorporate thin films materials into spintronic devices to reduce the switching energies without significant trade-offs in other performance metrics such as the thermal stability.

Lu’s other research may also be pertinent to C-SPIN. For a NSF-sponsored project, he is investigating the integration of MnAl and low damping Co₂FeAl (a Heusler alloy) into spin torque nano-oscillator structures. His group also regularly characterizes thermoelectric materials for a wide variety of projects.

Lu received his PhD degree in Materials Science from University of California Santa Barbara in 2006. He was a postdoc at the University for two years, then became a research track faculty member in 200. He has been a co-PI for Non-Volatile Logic project supported by DARPA, a PI in DTRA sponsored radiation effects in spintronic devices project, and a PI for a NSF-sponsored Spin Torque device project. He is a recipient of FEST award at the University of Virginia and the Edward C. Henry Award from the American Ceramic Society, and he has collaborated with C-SPIN PIs Bill Butler and Caroline Ross.

Welcome to C-SPIN, Prof. Lu!

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Announcing: Topological Spintronic Devices and Beyond Workshop

The first ever Topological Spintronic Device Workshop will be held at the University of Minnesota May 12-13 – directly following the internal C-SPIN mid-year review. The aim of the Workshop is to candidly discuss the promises and challenges of topological insulators that can accelerate the development of spintronic computing devices. Heterostructures that interface ferromagnets with materials with strong spin-orbit coupling will be a prime topic of conversation.

Jian-Ping Wang (University of Minnesota) and Nitin Samarth (Penn State) are organizing the workshop. The list of speakers including Nobel Laureate, Albert Fert, has been posted soon on the Workshop website. Registration information will be posted in the coming week.

It's hard to image right now, but winter is over in Minnesota by mid-May. Really – the average high is 70º. So save the date!

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Student and Post-Doc Profiles

Heidi Seinige

Ph.D. candidate at The University of Texas at Austin

I'm currently working on understanding the correlation between the orbital states, electronic transport properties, and magnetic properties in transition metal oxides such as antiferromagnetic Sr₂IrO₄ (Theme 4). Until now, antiferromagnetic materials have only been used as inactive components in spintronic devices – for example, as exchange biased layers in spin valves or magnetic tunnel junctions. But in the emerging field of antiferromagnetic spintronics, we’re thinking of them as active components. They offer ultra-fast switching schemes and they are insensitive to magnetic field perturbations (and therefore allow for higher memory density).

Before working with antiferromagnetic materials, I mostly worked with exchange-biased spin valves to understand their spin-transfer torque driven magneto-dynamics. We showed that spin-transfer torque is more efficient in spin valves with perpendicular and canted magnetization than in those with in-plane magnetization. We also showed that a high current bias can drive ferromagnetic resonance and non-linear excitations such as parametric resonance. This is very interesting from a fundamental point of view, but it may also be the foundation for faster magnetic switching and lower power consumption in future memory applications.

I’m fascinated by the way fundamental science shapes our everyday world. An easy example is the smart phone I carry around every day – just think about all the research and technology development behind that! And I am curious to see how today’s research at C-SPIN will affect the future. Will computers be primarily spin-based in 50 years? Or some kind of spin-CMOS hybrid? Or something else entirely?

After graduating, I would like to apply the knowledge and skills I learned as a graduate student in an industrial setting. My goal is to further understand how fundamental research affects real-life products and drive the improvement of computer technology.

Hamid Almasi

Ph.D. candidate at the University of Arizona

I am currently working on perpendicular magnetic tunnel junctions (p-MTJs), the building blocks for the vast majority of new spintronic computing devices. In particular, I am trying to simultaneously improve magneto-electric properties (such as PMA and TMR) and also device performance characteristics (such as thermal budget). This work is primarily under Theme 1 and Theme 4.

I am also studying the VCMA effect in pMTJs with interfacial PMA. Due to the nature of my work, we also provide high-quality MTJs for a number of other researchers in C-SPIN. I have several published and pending papers relevant to all of my research.

I had background in condensed matter physics, so I found Prof. Weigang Wang’s research fascinating both from a theoretical and application point of view. The most interesting part of this research is how it will be integrated into future electronic devices. I really enjoy being a part of the research that takes the science from the theoretical level and delivers an application for new levels of performance. With this in mind, I am hoping to see the emergence of new spintronic devices in the near future.

I hope to continue working in magnetic nanostructures and spintronic devices as a postdoctoral researcher in academia or industry after my graduation. I am really interested in learning new skills and expanding my knowledge in this field, and I aim to perform top-quality research which may lead to a breakthrough in the field. I eventually would like to lead my own research group in order to work on related topics in spintronics with a focus on device applications.