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Salamon, Myron B. Borchers, Julie Ann 2011-06-01T15:39:41Z 2011-06-01T15:39:41Z 10000-01-01 1990 "The magnetic and structural properties of crystalline erbium thin films and Er /Y superlattices, grown by Molecular Beam Epitaxy, have been analyzed by x-ray scattering, bulk magnetization measurements and neutron diffraction. By comparing the data for the two systems, the effects of the interfacial strain and the artificial modulation on the magnetic behavior of the Er have been determined. Specifically, the imposed secondary periodicity in the superlattices does not cause an interuption of the modulated Er spin order at the Er /Y interfaces. The CAM and basal plane spiral in these systems are coherent through the nonmagnetic yttrium interlayers. The primary differences between the magnetic behavior of bulk Er and both the films and superlattices are the absence of the Er ferromagnetic state, the enhancement of the critical fields and the reduction of the Neel temperatures. These effects follow directly from the epitaxial basal plane strain which is measurable in films over 14000A thick. This strain, along with a ""clamping"" of the Er thermal expansion to the Y lattice, leads to a reduction of the magnetoelastic energy that drives the ferromagnetic transition. The dependence of the magnetoelastic energy on the epitaxial strain is described by a model which accounts for the elastic coupling of the erbium lattice to the yttrium. In addition, the neutron diffraction and bulk magnetization measurements show that the sequence and stability of the c-axis commensurate states in bulk Er are altered in all of the samples considered. In the Er films, anomalies in the magnetization and wavevector data indicate that only the high temperature Er ""lock-in"" structures are formed. For the superlattices the CAM net moment state with four spins up followed by three spins down is stable over an extended temperature and field range. In addition, a new intermediate spin configuration with a net moment of ! the saturation moment develops in the superlattice with the thinnest Er interlayers. Variations in the nature of the Er c-axis modulation can qualitatively be explained by a modification of ·the relative exchange interaction between nearest-neighbor and next-nearest-neighbor spins in the context of the ANNNI model." Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-01T15:39:41Z No. of bitstreams: 1 1990_borchers.pdf: 6697455 bytes, checksum: cfa1ab9a293f5b764b1626582f5e8d22 (MD5) Made available in DSpace on 2011-06-01T15:39:41Z (GMT). No. of bitstreams: 1 1990_borchers.pdf: 6697455 bytes, checksum: cfa1ab9a293f5b764b1626582f5e8d22 (MD5) Previous issue date: 1990 Restriction data tranferred 2014-07-01T11:13:30-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-01T15:39:41Z Item is restricted indefinitely. Thesis U of I Only 3473804 http://hdl.handle.net/2142/25203 en 1990 Julie Ann Borchers crystalline erbium thin films Er/Y superlattices Molecular Beam Epitaxy interfacial strain Structural and magnetic properties of erbium thin films and Er/Y superlattices Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.