Condensed Matter Physics Seminar

Magnetic nanostructures are considered basic building blocks in spintronics and high-density data storage applications. Surface and configurational effects in oxide nanoparticle assemblies have been increasingly found to play significant roles in controlling the magnetic anisotropy. Modification of the surface spin structure in magnetic oxide nanoparticles can be achieved by methods such as controlling the particle shapes, use of mechanical milling or surfactant chemistry to alter the coordination of surface atoms and forming interfaces with non-magnetic metals. We discuss how these effects often lead to novel magnetic properties, useful for applications, such as tunable exchange bias and enhanced magnetocaloric effect (MCE). We will present dynamic radio-frequency (RF) transverse susceptibility as a powerful probe of surface and interface magnetism in nanostructures. We will also demonstrate MCE as a powerful tool to study first and second order phase transitions in complex oxides and discuss the influence of nanostructuring in mixed-phase manganites. Overall we will show how transverse susceptibility and MCE experiments have helped resolve finer aspects of the magnetic phase diagram in mixed-phase manganites leading to the emergence of a clearer understanding of the phase coexistence.

Research supported by National Science Foundation, Department of Energy and the Army Research Office