Meiere Symposium

Meiere Symposium on "Magnetism"
Friday, November 15
Lilly Auditorium (lower level of University Library on the IU Indianapolis campus)

Information and communications technology is predicted to account for 10% to 20% of the world’s power consumption within a decade. Alleviating this rise in power consumption requires rethinking the way we electronically process and store information. One promising route to develop energy-efficient storage/memory uses spintronic, or spin-electronic, devices.

In this talk, I will discuss a write mechanism for spintronic memories whereby a charge current manipulates a ferromagnetic layer’s magnetization through spin-orbit coupling. This mechanism, known as spin-orbit torque, is promising because it involves a transfer of angular momentum from the atomic lattice—a virtually infinite source of angular momentum—to the magnetic order. In this talk, we will summarize our prediction of novel spin-orbit torque mechanisms based on micromagnetic, semiclassical, and first principles calculations and argue that they are potentially important for devices such as nonvolatile magnetic memories, microwave generators, and neuromorphic computing.

Dr. Vivek Amin is an Assistant Professor in the Department of Physics at Indiana University Indianapolis.

He received a B.S. in Electrical Engineering from The University of Texas at Austin and a Ph.D. in Physics from Texas A&M University. Prior to joining IU Indianapolis, he worked as a postdoc and a research scientist with a joint position at the National Institute of Standards and Technology, Gaithersburg and the University of Maryland, College Park.

Prof. Amin uses computational and analytical methods to study electronic transport in condensed matter systems, with focus on spintronics, quantum materials, and neuromorphic computing.

As the expectations for novel electronics grow, the design of flexible and high-density nonvolatile molecular memory devices remains a hot topic. Voltage control of "molecular spintronics" (where charge and spin both matter) is a major goal because such nonvolatile molecular structures have the very real possibility of providing a room temperature nonvolatile device on a length scale less than 10 nm (semiconductor industry goals), while delivering low power GHz nonvolatile local logic or memory operations. The successes in addressing the grand challenge of manipulating magnetically ordered states by electrical approach suggest new routes to developing novel spintronics.

While much is in its infancy, molecular spintronics has now been shown to be possible. The spin crossover (SCO) phenomenon, in 3d transition metal compounds, through the manipulation of interfacial chemistry, can be exploited to create voltage-controlled isothermal changes in the electronic structure. This has been shown for the Fe (II) spin crossover complexes interfaced with molecular ferroelectrics. This nonvolatile isothermal voltage-controlled switching, at room temperature, is evident in both spectroscopy and transport studies of thin film bilayer devices. This comes at a lower energy cost and at faster speeds and far less fabrication complexity than the currently commercially available nonvolatile memory based on magnetic tunnel junctions.

But there are challenges still to be addressed. The key problem of the high impedance of the device has now been addressed through chemistry. The key take-away point is that molecular nonvolatile room temperature "memory" devices have been realized and new developments in chemistry should lead to better molecular nonvolatile electronic devices.

Ruihua Cheng is currently working at the Department of Physics of Indiana University Indianapolis as a professor.

She received her Ph.D in Physics from the University of Nebraska-Lincoln in 2002. She then conducted postdoctoral research in the Magnetic Thin Film group of the Materials Science Division at Argonne National Laboratory. In 2005, she joined the Department of Physics at IU Indianapolis.

Her current research is focused on the characterization of molecular magnetic materials, particularly spin crossover molecular manipulation and their applications in molecular based devices. Her research work has been funded by multiple grants from NSF.

The Earth’s magnetic field is not only an incredible natural phenomenon responsible for such wonders as the aurora borealis and for supporting navigation during the age of discovery, but it is also a useful tool for understanding the inner workings of our planet.

We will start our journey in the Earth’s convecting outer core that is likely generating our magnetic field and explore some ways that our core and magnetic field are unique in our solar system.

Then we will look at how some unique behaviors of our magnetic field recorded in rocks in the oceanic crust revolutionized our understanding of the surface of the Earth.

Last we will talk about some ways that magnetic fabrics and anomalies can be a useful tool for understanding magmatism and volcanic hazards on planet Earth.

I completed my Ph.D. in Geological Sciences at the University of Missouri-Columbia in 2021 in high-temperature experimental volcanology before starting my post doc with Dr. Catherine “Cam” Macris at IUPUI (now IU Indianapolis) in October 2021. I transitioned to a visiting lecturer in Fall 2022 and was recently hired permanently as a lecturer in the Department of Earth and Environmental Sciences at IU Indianapolis in the Fall of 2024.