Research Areas

Our group focuses on the study of novel ground states and functional properties in condensed matter systems synthesized via atomically precise thin film deposition techniques. These model systems often provide for ground states and functional properties not observable in the bulk. Our recent emphasis has been on highly correlated electronic systems, especially new spintronic materials that address fundamental questions that still exist in magnetism. Projects have also included the development of spin polarized devices, and more recently, spin current generation based on complex oxide thin films. We are also developing low dimensional metallic systems at oxide interfaces. Nanofabrication is used to study functional properties at the nano-scale as well as to fabricate new classes of nano-scale devices.

Research projects include:

Emergent Magnetic Phenomena at Interfaces

Controlling collective phenomena and emergent properties at interfaces often leads to new ground states not attainable in their bulk constituents. By designing and perfecting atomic level synthesis of materials with rich phase diagrams in the bulk, we explore new classes of complex oxide interface systems. These systems provide for quasi-two-dimensional model systems with spin functionality in which we can address fundamental questions about the nature of magnetism at surfaces and interfaces but also provide promising new materials for a more energy efficient spin based electronics.

One recent example of this emergent magnetic behavior is the observation of interfacial ferromagnetism between an antiferromagnetic insulator and paramagnetic metal in the CaMnO3/CaRuO3 superlattice system. (See C.He et al., Phys. Rev. Lett. 109 197202 (2012))

Transmission electron microscopy image of a CaRuO3/CaMnO3 superlattice. We demonstrate that the interfacial ferromagnetism is due to a double exchange mechanism attributed to the leakage of itinerant electrons from CaRuO3 into CaMnO3 ine on unit cell at the interfaces through exchange bias, polarized neutron reflectivity and scanning transmission electron microscopy/ electron energy loss spectroscopy measurements.

 

New Ground States via Coherent Epitaxial Strain

Strongly correlated materials exhibit a wide range of electronic and magnetic ground states that are a manifestation of competing interactions of charge, spin, lattice and orbital degrees of freedom. The rich phase diagrams of many of these materials provide model systems for the tuning and control of these ground states via epitaxial strain. The epitaxial strian can modify the electronic and magnetic structure of the thin film material, especially in those materials which are on the verge of a phases transition.

For example, we have been able to stabilize metallic ground states in correlated materials that are insulating in the bulk but on the verge of a metal-insulator transition in LaTiO3 films on SrTiO3 substrates. (See C. He et al., Phys. Rev. B 86 081401 (2012))

Another example is the stabilization of a ferromagnetic ground state in LaCoO3 which does not exhibit any long range magnetic order in the bulk. Our recent collaborative effort has found that the ferromagnetism can be explained in terms of long range ferromagnetic order mediated by oxygen vacancy ordering.

Transmission electron microscopy image of a LaCoO3 film on SrTiO3 substrate show oxygen vacancy ordering in the form of dark striped perpendicular to the film/ substrate interface. These films exhibit a saturated magnetic moment of 0.85┬ÁB/Co ion and Tc of 85K although bulk LaCoO3 does not show any evidence of long range ferromagnetic order.

 

 


Suzuki Lab
171 Moore Building
Stanford, CA 94305-4045
Fun fact: Though redwoods are perennial, each year the Stanford Tree Mascot costume is built anew. Lab Phone: (650) 723-1668

Last updated: September 2016