Novel magnetic behavior in heavy rare earth superlattices

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6986801

Tsui, Tien Fang

Structural and magnetic properties of heavy rare earth films and superlattices synthesized by molecular beam epitaxy are investigated. Epitaxial films of rare earth metals, and superlattices of rare earths with Y interlayers, are grown along different hcp orientations using novel techniques developed specifically for this thesis research. Magnetic behavior is explored by neutron diffraction and SQUID magnetometry experiments. The spatial form of the exchange interaction is explored by probing the dependence of magnetic coherence on crystal growth orientation. The results reveal that Dy/Y and Gd/Y superlattices grown along the a and b axis exhibit weak magnetic coupling between successive magnetic layers. This measured anisotropy between behavior along the c-axis and perpendicular to it, is over a factor ten in both the coupling strength and the range. The strongly anisotropic coupling behavior is shown to have its origin in nearly 2-dimensional nesting features of the rare earth Fermi surfaces. Nesting along the c-axis gives rise to long range exchange interactions along the c-axis, and the lack of nesting perpendicular to the c-axis leaves a rapid exponential decay of the exchange with spin separation. Magnetic phases of epitaxial Dy films are examined as a function of epitaxial strain, growth orientation, temperature and field. The analysis of the observed anisotropic magnetoelastic behavior reveals the detailed energy balance in the Dy system. The observed spin configurations in thin Gd films show that the magnetocrystalline anisotropy of bulk Gd is substantially modified in the films. This in turn gives insight into the origin of the unusual spin reorientation transition in Gd. Magnetic order in buried monolayers of Gd-Y alloys is studied in order to explore the effects of both the reduced physical dimensions and the modified effective exchange interaction on phase transitions.

• Research Organization: Illinois Univ., Urbana, IL (United States)
• OSTI ID: 6986801
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360104* -- Metals & Alloys-- Physical Properties
ALLOYS
CRYSTAL STRUCTURE
DYSPROSIUM ALLOYS
EPITAXY
FILMS
GADOLINIUM ALLOYS
MAGNETIC PROPERTIES
MOLECULAR BEAM EPITAXY
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
SUPERLATTICES
THIN FILMS
YTTRIUM ALLOYS