News

Peter gives a talk at MS&T 2018

October 15, 2018 By Peter Meisenheimer

Peter gives a talk on the magnetism of entropy-stabilized oxides at MS&T 2018 in Columbus, OH, entitled Structurally Driven Magnetic Disorder in Entropy-Stabilized Oxides.

Abstract: A unique benefit to entropic stabilization is the increased solubility of elements, which opens a broad compositional space with subsequent local chemical and structural disorder resulting from different atomic sizes and preferred coordinations of the constituents. In the antiferromagnetic entropy-stabilized oxides studied here, we see that by tuning the chemistry, and thus the concentration of local structural distortions, we can either induce or reclaim a large degree of frustration in the magnetic lattice of the material. This effect can then be engineered to enhance the strength of the magnetic exchange field by a factor of 10x in ferromagnetic/antiferromagnetic heterostructures, when compared to a “normal” antiferromagnetic oxide, such as CoO. Our results reveal that the unique characteristics of entropy stabilized materials can be utilized to engineer and enhance magnetic functional phenomena in oxide thin films, as well as offer a powerful platform for the study of defects and functional properties.

Sieun passes candidacy exam!

September 21, 2018 By Peter Meisenheimer

Congratulations to Sieun for passing her candidacy exam on September 4th.

Doping is an essential step in semiconductor technology to achieve the desired type and level of electrical conductivity. Thus, predicting both n-type or p-type dopability of a material is a prerequisite to exploit the material for electronic application. First-principles calculations are a powerful tool to understand point-defect properties since experimental studies to identify and characterize defects at the atomic scale are challenging. To predict n-type and p-type dopability of an unexplored wide bandgap material, we investigated the thermal stability and charge state of various intentional dopants, the issues regarding carrier localization, and charge compensation from native defects.

New Article! “Electric and magnetic domains inverted by a magnetic field”

August 23, 2018 By Peter Meisenheimer

“The ability to use an electric or magnetic field to manipulate the orientation of electric dipoles or magnetic moments associated with atoms, ions or molecules in a material provides a vast array of functions. In rare materials called magnetoelectric multiferroics, the dipoles are intimately coupled to the moments, and a single field can control both¹. After the field is applied, however, the dipoles and moments typically all have the same orientation, and the original pattern that they formed is lost. In a paper Nature, Leo et al.² show that, in two particular materials, a magnetic field can flip each of the dipoles or moments while preserving the structure of the original pattern. The work illustrates how the complex coupling in these materials could be used to uncover other, previously unobserved electric and magnetic effects.”

Full text available from Nature

Congratulations to Peter for his Rackham Graduate Student Research grant.

July 9, 2018 By Peter Meisenheimer

Peter received a Rackham Graduate Student Research grant for $3,000 to go towards the purchase of a top-of-the-line isolation system for the AFM. Congratulations!

New Publication! “Perspective: Magnetoelectric switching in thin film multiferroic heterostructures”

June 22, 2018 By Peter Meisenheimer

New Publication!- P. B. Meisenheimer, S. Novakov, N. M. Vu, J. T. Heron Journal of Applied Physics 123, 240901 (2018).

Abstract: Since the resurgence of multiferroics research, significant advancement has been made in the theoretical and experimental investigation of the electric field control of magnetization, magnetic anisotropy, magnetic phase, magnetic domains, and Curie temperature in multiferroic heterostructures. As a result of these advances, multiferroic heterostructures are on a trajectory to impact spintronics applications through the significantly reduced energy consumption per unit area for magnetization switching (1–500 μJ cm⁻²) when compared to that of current-driven magnetization switching (0.2–10 mJ cm⁻²). Considering this potential impact, it becomes necessary to understand magnetoelectric switching dynamics and characteristic switching times. The body of experimental work investigating magnetoelectric switching dynamics is rather limited, with the majority of room temperature converse magnetoelectric switching measurements reported having employed relatively long voltage pulses. Recently, however, the field has started to consider the kinetics of the switching path in multiferroic (and ferroelectric) switching. Excitingly, the results are challenging our understanding of switching processes while offering new opportunities to engineer the magnetoelectric effect. Considering the prospects of multiferroics for beyond-CMOS applications and the possible influence on operational speed, much remains to be understood regarding magnetoelectric switching kinetics and dynamics, particularly at reduced dimensions and under the influence of boundary effects resulting from strain, electrostatics, and orientation. In this article, we review magnetoelectric switching in multiferroic heterostructures for the electric field control of magnetism. We then offer perspectives moving toward the goal of low energy-delay spintronics for computational applications.