Ping WangFollow

Document Type



Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor's Name

Sakhrat Khizroev

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Jean H. Andrian

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Stavros V. Georgakopoulos

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Pezhman Mardanpour

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Dwayne McDaniel

Fifth Advisor's Committee Title

Committee Member

Sixth Advisor's Name

Osama A. Mohammed

Sixth Advisor's Committee Title

Committee Member


Colossal Magnetoelectric Effect, CoFe2O4-BaTiO3, NiFe2O4-BaTiO3, Coreshell Nanostructures, Magnetoelectric Nanoparticles

Date of Defense



The greatly increased interest in magnetoelectric materials over the last decade is due to their potential to enable next-generation multifunctional nanostructures required for revolutionizing applications spanning from energy-efficient information processing to medicine. Magnetoelectric nanomaterials offer a unique way to use a voltage to control the electron spin and, reciprocally, to use remotely controlled magnetic fields to access local intrinsic electric fields. The magnetoelectric coefficient is the most critical indicator for the magnetoelectric coupling in these nanostructures. To realize the immense potential of these materials, it is necessary to maximize the coefficient. Therefore, the goal of this PhD thesis study was to create a new paradigm for the synthesis and characterizations of magnetoelectric materials which would allow to create a new dynasty of nanostructures required for unlocking all their unprecedented capabilities. Coreshell nanostructures with a 0-3 connectivity scheme, i.e. (Co, Ni) Fe2O4-BaTiO3, represent the most studied system. Their relatively low coefficient value is often attributed to the problem known as the dielectric leakage, which is present during the traditional powder form measurements of the coefficient. To overcome this problem, we implemented a novel approach to measure the coefficient at a single-nanoparticle level. Using a scanning probe microscopy, we entirely eliminated the interparticle interaction and thus the leakage problem. The success of this approach was underscored by achieving, for the first time, perfect crystal lattice matching between the magnetostrictive core and the piezoelectric shell of the coreshell configuration, as confirmed via transmission electron microscopy. As a result, this study led to the coefficient value for CoFe2O4-BaTiO3 nanoparticles of above 5 V cm-1 Oe-1, almost two orders of magnitude higher than the highest reported value elsewhere. Additionally, we for the first time demonstrated three different regions which are barium titanate shell, the interfacial transition, and the cobalt ferrite core, respectively, by imaging a half-grown coreshell nanoparticle with atomic force microscopy. Alternating gradient and cryogenic vibrating sample magnetometry were utilized to study the magnetic properties of materials. X-ray diffraction was employed to bespeak that the crystallinity of barium titanate is enhanced along with the increase of cobalt ferrite dopant on account of heterogeneous nucleation.





Previously Published In

Wang, P., Zhang, E., Toledo, D., Smith, I. T., Navarrete, B., Furman, N., ... & Khizroev, S. (2020). Colossal Magnetoelectric Effect in Coreshell Magnetoelectric Nanoparticles. Nano Letters.



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