Magnetic phase diagram of Ho/Er alloys
| Autor: | J.A. Simpson, C. Bryn-Jacobsen, M. R. Wells, D. F. McMorrow, R. C. C. Ward, R A Cowley |
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| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Physical Review B. 57:8394-8407 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.57.8394 |
| Popis: | The magnetic structures of a series of Ho/Er alloys have been determined by neutron-diffraction techniques. The alloys were prepared as thin films (10000 Angstrom thick) by molecular beam epitaxy, and are single crystals with a mosaic spread of about 0.2 degrees. A variety of magnetic structures are found, arising from the competition between the exchange and anisotropic crystal-field interactions, the latter of which are of opposite sign for Ho and Er. The magnetic phase diagram has five distinct phases with long-range magnetic order: basal-plane helical, tilted helical, cycloidal, c-axis longitudinally modulated, and conical. The cycloid and tilted helix have both incommensurate and commensurate q = 1/4c* forms, and all of the thin films have a conical structure at low temperatures, even though corresponding films of pure Ho and Er do not exhibit this phase. There is a pentacritical point, and probably a disordered phase which is completely surrounded in the phase diagram by magnetic phases with long-range order. A Landau theory is developed to describe these results. |
| Databáze: | OpenAIRE |
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