Magnetic properties of the rare earth systems neodymium/yttrium and dysprosium/yttrium
Everitt, Brenda Anne
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https://hdl.handle.net/2142/22155
Description
Title
Magnetic properties of the rare earth systems neodymium/yttrium and dysprosium/yttrium
Author(s)
Everitt, Brenda Anne
Issue Date
1995
Doctoral Committee Chair(s)
Salamon, Myron B.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Language
eng
Abstract
We have studied a series of Nd/Y films and superlattices, grown by molecular beam epitaxy (MBE), using neutron, x-ray, and bulk magnetization techniques. These epitaxial Nd/Y systems are the first to be grown and studied which incorporate a light rare earth (RE) element. Using neutron diffraction, we have found that a portion of the Nd moment in the superlattices orders in a c-axis helical phase that does not exist in bulk. The helimagnetic turn angle decreases from $\rm{\sim}60\sp\circ$/atomic layer just below T$\rm\sb{N},$ to nearly antiferromagnetic coupling between same-symmetry site layers (90$\sp\circ$/at. layer) in the low-temperature limit. The ordering temperature of the helimagnetic phase is $\sim$30 K, an enhancement of about 50% over the bulk T$\rm \sb{N}$ of 19.9 K. As the Nd films or superlattice interlayers become thicker, the magnetic moments of the sample increasingly tend to order in basal-plane modulated phases, similar to those seen in bulk; for a thick 5825 A Nd film, only basal-plane modulated magnetic order was observed. We expect that the formation of the c-axis helical phase in the Nd/Y superlattices is due to hybridization of the band structure in these systems, rather than to epitaxial strain-induced effects. We have also studied a heavy RE allow using x-ray resonant magnetic scattering. We have used this technique to detect, for the first time, the presence of the induced spin-density wave in the conduction band of nonmagnetic Lu atoms which are alloyed in a helimagnetic Dy host lattice. By tuning the incident synchrotron x-ray energy to the L$\rm\sb{III}$ edges of both Dy and Lu, we were able to use the species-sensitivity of x-ray resonant magnetic scattering to isolate the contribution from each element individually. As there are no unfilled f-levels on Lu atoms, the intensity observed at the magnetic wavevector that is resonant at the Lu edge reflects the polarization of the 5d electrons, which support a spin-density wave of $\rm{\sim}0.1\ \mu\sb{B}/$atom in the Dy$\sb{0.6}$Lu$\sb{0.4}$ thin film alloy.
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