Degree Granting Department
Casey W. Miller, Ph.D.
Dale Johnson, Ph.D.
Gerald Woods, Ph.D.
Magnetocaloric effect, nanostructuring, magnetic entropy
The standard material by which all materials exhibiting magnetocaloric effect are
measured is Gadnolinium. In this work we are attempting to understand how
nanostructuring can impact the magnetocaloric effect, to this end we have grown Gd in
various thin film structures. The samples made were grown via magnetron sputtering on
MgO(100) substrates. Samples of thick Gd (2000 A) were grown and sandwiched
between two layers of Cr or W and annealed at increasing temperatures to study how this
can perturb the magnetic and structural properties of the Gd. Another set of samples was
grown in which Gd (at various thicknesses) is in a multilayer system with W. Here the
purpose is to explore how changing the thickness of the Gd can change its magnetic
properties. Using the appropriate Maxwell relation, the magnetic entropy change was
observed to increase with increasing annealing temperature. In a 0-4T magnetic field
change, the peak entropy was found to go from approximately 1.5 J/kg-K for the
unannealed sample to 4.4 J/kg-K when annealed to 600°C. The multilayers were found
to all have a T
C near 280 K, in contrast with what is predicted by finite size scaling. This
is likely due to pinholes in the W layers allowing the Gd to act as one magnetic material.
Scholar Commons Citation
Williams, Daryl V. Jr., "Characterization of the Structural and Magnetic Properties of Gd Thin Films" (2010). USF Tampa Graduate Theses and Dissertations.