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.

“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

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!- 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.

Full text available from Journal of Applied Physics

New Publication!- S. Sivakumar*, E. Zwier*, P. B. Meisenheimer*, J. T. Heron J. Vis. Exp. (135), e57746, (2018).

Abstract: Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

Full text available from Journal of Visualized Experiments