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Physics Program presents

Investigating Spin Frustration within Thin-Film Magnetic Oxides

Tuesday, November 12, 2013

A lecture by
Jarrett Moyer
Candidate for the position in Physics

Transition-metal complex oxides are ideal systems for studying condensed matter physics due the wide variety of novel phenomena that they can display, such as high temperature superconductivity, colossal magnetoresistance, and multiferroicity.  Their magnetic properties can often be tuned through small variations in chemical doping, strain, or thickness.  This makes oxides promising for use in nextgeneration device applications, in which the magnetism will be controlled by external factors other than magnetic fields.  A relatively unexplored method to induce large changes in the magnetization is to control the degree of spin frustration within a frustrated magnetic oxide.  In this talk, I will discuss recent magnetic spectroscopy measurements on the magnetic structure of iron-doped cobalt ferrite (Co1xFe2+xO4).  We observed that as the degree of iron doping increases, there is a large, non-linear increase in the magnetization that is partially caused by a decrease in the spin frustration of the divalent cations.  This change in spin frustration is a direct result of the Co2+Fe3+ exchange interactions having different strengths than the corresponding Fe2+-Fe3+ exchange interaction.  I will propose a second, reversible method of controlling this spin frustration: the application of an electric field to the spinel ferrite.  Under an applied electric field, the mobile electrons within the ferrite will rearrange themselves to screen the field, and, in effect, this will change the ordering of the magnetic cations.  This will alter the frustration within the film, thus allowing the degree of frustration and the magnetization to be controlled with an electric field.  To make this device non-volatile, the electric field can be applied with an adjacent ferroelectric layer.  I will conclude this talk by discussing recent work on the integration of Fe3O4 with perovskites, which is the first step towards achieving non-volatile, electrically driven magnetic switching in a ferroelectric perovskite/spinel ferrite heterostructure.

Location: RKC 115